diff --git a/man/shadowsocks-libev.8 b/man/shadowsocks-libev.8
index aa0ae18f..5a6a47a4 100644
--- a/man/shadowsocks-libev.8
+++ b/man/shadowsocks-libev.8
@@ -164,6 +164,9 @@ Only available in manager mode.
 .TP
 .B \-v
 Enable verbose mode.
+.TP
+.B \-h, --help
+Print help message.
 
 .SH EXAMPLE
 \*(Re requires netfilter's NAT function. Here is an example:
diff --git a/man/ss-local.1 b/man/ss-local.1
index 3c7007c6..9a35d7c3 100644
--- a/man/ss-local.1
+++ b/man/ss-local.1
@@ -31,11 +31,11 @@ ss-local \- shadowsocks client as socks5 proxy, libev port
 
 .SH SYNOPSIS
 \*(Lo
-    [\fB\-Auhv\fR]
+    [\fB\-Auv\fR]           [\fB\-h\fR|\fB\--help\fR]
     [\fB\-s\fR \fIserver_host\fR] [\fB\-p\fR \fIserver_port\fR]    [\fB\-l\fR \fIlocal_port\fR]
     [\fB\-k\fR \fIpassword\fR]    [\fB\-m\fR \fIencrypt_method\fR] [\fB\-f\fR \fIpid_file\fR]   [\fB\-t\fR \fItimeout\fR]
     [\fB\-c\fR \fIconfig_file\fR] [\fB\-b\fR \fIinterface\fR]      [\fB\-a\fR \fIuser_name\fR]
-    [\fB\-n\fR \fInofile\fR]      [\fB\-\-fast\-open\fR]    [\fB\-\-acl\fR \fIacl_config\fR]
+    [\fB\-n\fR \fInofile\fR]      [\fB\-\-fast\-open\fR]       [\fB\-\-acl\fR \fIacl_config\fR]
 
 .SH DESCRIPTION
 \*(Me is a lightweight and secure socks5 proxy. It is a port of the original
@@ -110,6 +110,9 @@ Enable ACL (Access Control List) and specify config file.
 .TP
 .B \-v
 Enable verbose mode.
+.TP
+.B \-h, --help
+Print help message.
 
 .SH EXAMPLE
 \*(Lo(1) can be started from command line and run in foreground. Here is an
diff --git a/man/ss-manager.1 b/man/ss-manager.1
index 00902398..cab021a8 100644
--- a/man/ss-manager.1
+++ b/man/ss-manager.1
@@ -32,7 +32,7 @@ statistics
 
 .SH SYNOPSIS
 \*(Ma
-    [\fB\-AhuUv\fR]
+    [\fB\-AuUv\fR]          [\fB\-h\fR|\fB\--help\fR]
     [\fB\-s\fR \fIserver_host\fR] [\fB\-p\fR \fIserver_port\fR]     [\fB\-l\fR \fIlocal_port\fR]
     [\fB\-k\fR \fIpassword\fR]    [\fB\-m\fR \fIencrypt_method\fR]  [\fB\-f\fR \fIpid_file\fR]
     [\fB\-t\fR \fItimeout\fR]     [\fB\-c\fR \fIconfig_file\fR]     [\fB\-i\fR \fIinterface\fR]
@@ -119,6 +119,9 @@ Only available in manager mode.
 .TP
 .B \-v
 Enable verbose mode.
+.TP
+.B \-h, --help
+Print help message.
 
 .SH PROTOCOL
 \*(Ma(1) provides several APIs through UDP protocol:
diff --git a/man/ss-redir.1 b/man/ss-redir.1
index 244798ac..5b85e0bd 100644
--- a/man/ss-redir.1
+++ b/man/ss-redir.1
@@ -31,7 +31,7 @@ ss-redir \- shadowsocks client as transparent proxy, libev port
 
 .SH SYNOPSIS
 \*(Re
-    [\fB\-AhuUv\fR]
+    [\fB\-AuUv\fR]          [\fB\-h\fR|\fB\--help\fR]
     [\fB\-s\fR \fIserver_host\fR] [\fB\-p\fR \fIserver_port\fR]    [\fB\-l\fR \fIlocal_port\fR]
     [\fB\-k\fR \fIpassword\fR]    [\fB\-m\fR \fIencrypt_method\fR] [\fB\-f\fR \fIpid_file\fR]
     [\fB\-t\fR \fItimeout\fR]     [\fB\-c\fR \fIconfig_file\fR]    [\fB\-b\fR \fIlocal_address\fR]
@@ -105,6 +105,9 @@ Enable onetime authentication.
 .TP
 .B \-v
 Enable verbose mode.
+.TP
+.B \-h, --help
+Print help message.
 
 .SH EXAMPLE
 \*(Re requires netfilter's NAT function. Here is an example:
diff --git a/man/ss-server.1 b/man/ss-server.1
index 9b699cbd..6b952640 100644
--- a/man/ss-server.1
+++ b/man/ss-server.1
@@ -31,7 +31,7 @@ ss-server \- shadowsocks server, libev port
 
 .SH SYNOPSIS
 \*(Se
-    [\fB-AhuUv\fR]
+    [\fB-AuUv\fR]          [\fB\-h\fR|\fB\--help\fR]
     [\fB\-s\fR \fIserver_host\fR] [\fB\-p\fR \fIserver_port\fR]    [\fB\-l\fR \fIlocal_port\fR]
     [\fB\-k\fR \fIpassword\fR]    [\fB\-m\fR \fIencrypt_method\fR] [\fB\-f\fR \fIpid_file\fR]
     [\fB\-t\fR \fItimeout\fR]     [\fB\-c\fR \fIconfig_file\fR]    [\fB\-i\fR \fIinterface\fR]
@@ -122,6 +122,9 @@ Only available in server and manager mode.
 .TP
 .B \-v
 Enable verbose mode.
+.TP
+.B \-h, --help
+Print help message.
 
 .SH EXAMPLE
 It is recommended to use a config file when starting \*(Se(1).
diff --git a/man/ss-tunnel.1 b/man/ss-tunnel.1
index 89f0d579..72e4997b 100644
--- a/man/ss-tunnel.1
+++ b/man/ss-tunnel.1
@@ -31,7 +31,7 @@ ss-tunnel \- shadowsocks tools for local port forwarding, libev port
 
 .SH SYNOPSIS
 \*(Tu
-    [\fB-AhuUv\fR]
+    [\fB-AuUv\fR]          [\fB\-h\fR|\fB\--help\fR]
     [\fB\-s\fR \fIserver_host\fR] [\fB\-p\fR \fIserver_port\fR]    [\fB\-l\fR \fIlocal_port\fR]
     [\fB\-k\fR \fIpassword\fR]    [\fB\-m\fR \fIencrypt_method\fR] [\fB\-f\fR \fIpid_file\fR]
     [\fB\-t\fR \fItimeout\fR]     [\fB\-c\fR \fIconfig_file\fR]    [\fB\-i\fR \fIinterface\fR]
@@ -111,6 +111,9 @@ Only used and available in tunnel mode.
 .TP
 .B \-v
 Enable verbose mode.
+.TP
+.B \-h, --help
+Print help message.
 
 .SH SEE ALSO
 .BR \*(Lo (1),
diff --git a/src/local.c b/src/local.c
index 12b1a67e..8eb97430 100644
--- a/src/local.c
+++ b/src/local.c
@@ -985,8 +985,9 @@ int main(int argc, char **argv)
 
     int option_index                    = 0;
     static struct option long_options[] = {
-        { "fast-open", no_argument,       0, 0 },
-        { "acl",       required_argument, 0, 0 },
+        { "fast-open", no_argument      , 0, 0 },
+        { "acl"      , required_argument, 0, 0 },
+        { "help"     , no_argument      , 0, 0 },
         {           0,                 0, 0, 0 }
     };
 
@@ -995,10 +996,10 @@ int main(int argc, char **argv)
     USE_TTY();
 
 #ifdef ANDROID
-    while ((c = getopt_long(argc, argv, "f:s:p:l:k:t:m:i:c:b:a:n:P:uvVA",
+    while ((c = getopt_long(argc, argv, "f:s:p:l:k:t:m:i:c:b:a:n:P:huvVA",
                             long_options, &option_index)) != -1) {
 #else
-    while ((c = getopt_long(argc, argv, "f:s:p:l:k:t:m:i:c:b:a:n:uvA",
+    while ((c = getopt_long(argc, argv, "f:s:p:l:k:t:m:i:c:b:a:n:huvA",
                             long_options, &option_index)) != -1) {
 #endif
         switch (c) {
@@ -1008,6 +1009,9 @@ int main(int argc, char **argv)
             } else if (option_index == 1) {
                 LOGI("initialize acl...");
                 acl = !init_acl(optarg, BLACK_LIST);
+            } else if (option_index == 2) {
+                usage();
+                exit(EXIT_SUCCESS);
             }
             break;
         case 's':
@@ -1058,6 +1062,9 @@ int main(int argc, char **argv)
         case 'v':
             verbose = 1;
             break;
+        case 'h':
+            usage();
+            exit(EXIT_SUCCESS);
         case 'A':
             auth = 1;
             break;
@@ -1069,6 +1076,10 @@ int main(int argc, char **argv)
             prefix = optarg;
             break;
 #endif
+        case '?':
+            // The option character is not recognized.
+            opterr = 1;
+            break;
         }
     }
 
diff --git a/src/manager.c b/src/manager.c
index c2dc7b47..f43d3e82 100644
--- a/src/manager.c
+++ b/src/manager.c
@@ -572,10 +572,11 @@ int main(int argc, char **argv)
 
     int option_index                    = 0;
     static struct option long_options[] = {
-        { "fast-open",       no_argument,       0, 0 },
-        { "acl",             required_argument, 0, 0 },
+        { "fast-open"      , no_argument      , 0, 0 },
+        { "acl"            , required_argument, 0, 0 },
         { "manager-address", required_argument, 0, 0 },
-        { "executable",      required_argument, 0, 0 },
+        { "executable"     , required_argument, 0, 0 },
+        { "help"           , no_argument      , 0, 0 },
         {                 0,                 0, 0, 0 }
     };
 
@@ -583,7 +584,7 @@ int main(int argc, char **argv)
 
     USE_TTY();
 
-    while ((c = getopt_long(argc, argv, "f:s:l:k:t:m:c:i:d:a:uUvA",
+    while ((c = getopt_long(argc, argv, "f:s:l:k:t:m:c:i:d:a:huUvA",
                             long_options, &option_index)) != -1)
         switch (c) {
         case 0:
@@ -595,6 +596,9 @@ int main(int argc, char **argv)
                 manager_address = optarg;
             } else if (option_index == 3) {
                 executable = optarg;
+            } else if (option_index == 4) {
+                usage();
+                exit(EXIT_SUCCESS);
             }
             break;
         case 's':
@@ -638,9 +642,16 @@ int main(int argc, char **argv)
         case 'v':
             verbose = 1;
             break;
+        case 'h':
+            usage();
+            exit(EXIT_SUCCESS);
         case 'A':
             auth = 1;
             break;
+        case '?':
+            // The option character is not recognized.
+            opterr = 1;
+            break;
         }
 
     if (opterr) {
diff --git a/src/redir.c b/src/redir.c
index 187e55a2..3f6f88f7 100644
--- a/src/redir.c
+++ b/src/redir.c
@@ -36,6 +36,7 @@
 #include <strings.h>
 #include <time.h>
 #include <unistd.h>
+#include <getopt.h>
 #include <limits.h>
 #include <linux/if.h>
 #include <linux/netfilter_ipv4.h>
@@ -671,10 +672,23 @@ int main(int argc, char **argv)
     ss_addr_t remote_addr[MAX_REMOTE_NUM];
     char *remote_port = NULL;
 
+    int option_index                    = 0;
+    static struct option long_options[] = {
+        { "help", no_argument, 0, 0 },
+        {      0,           0, 0, 0 }
+    };
+
     opterr = 0;
 
-    while ((c = getopt(argc, argv, "f:s:p:l:k:t:m:c:b:a:n:uUvA")) != -1)
+    while ((c = getopt_long(argc, argv, "f:s:p:l:k:t:m:c:b:a:n:huUvA",
+                            long_options, &option_index)) != -1) {
         switch (c) {
+        case 0:
+            if (option_index == 0) {
+                usage();
+                exit(EXIT_SUCCESS);
+            }
+            break;
         case 's':
             if (remote_num < MAX_REMOTE_NUM) {
                 remote_addr[remote_num].host   = optarg;
@@ -723,10 +737,18 @@ int main(int argc, char **argv)
         case 'v':
             verbose = 1;
             break;
+        case 'h':
+            usage();
+            exit(EXIT_SUCCESS);
         case 'A':
             auth = 1;
             break;
+        case '?':
+            // The option character is not recognized.
+            opterr = 1;
+            break;
         }
+    }
 
     if (opterr) {
         usage();
diff --git a/src/server.c b/src/server.c
index 1d96d00a..ec94ac65 100644
--- a/src/server.c
+++ b/src/server.c
@@ -1316,9 +1316,10 @@ int main(int argc, char **argv)
 
     int option_index                    = 0;
     static struct option long_options[] = {
-        { "fast-open",       no_argument,       0, 0 },
-        { "acl",             required_argument, 0, 0 },
+        { "fast-open"      , no_argument      , 0, 0 },
+        { "acl"            , required_argument, 0, 0 },
         { "manager-address", required_argument, 0, 0 },
+        { "help"           , no_argument      , 0, 0 },
         {                 0,                 0, 0, 0 }
     };
 
@@ -1326,8 +1327,8 @@ int main(int argc, char **argv)
 
     USE_TTY();
 
-    while ((c = getopt_long(argc, argv, "f:s:p:l:k:t:m:c:i:d:a:n:uUvAw",
-                            long_options, &option_index)) != -1)
+    while ((c = getopt_long(argc, argv, "f:s:p:l:k:t:m:c:i:d:a:n:huUvAw",
+                            long_options, &option_index)) != -1) {
         switch (c) {
         case 0:
             if (option_index == 0) {
@@ -1338,6 +1339,9 @@ int main(int argc, char **argv)
                 acl_path = optarg;
             } else if (option_index == 2) {
                 manager_address = optarg;
+            } else if (option_index == 3) {
+                usage();
+                exit(EXIT_SUCCESS);
             }
             break;
         case 's':
@@ -1389,13 +1393,21 @@ int main(int argc, char **argv)
         case 'v':
             verbose = 1;
             break;
+        case 'h':
+            usage();
+            exit(EXIT_SUCCESS);
         case 'A':
             auth = 1;
             break;
         case 'w':
             white_list = 1;
             break;
+        case '?':
+            // The option character is not recognized.
+            opterr = 1;
+            break;
         }
+    }
 
     if (opterr) {
         usage();
diff --git a/src/tunnel.c b/src/tunnel.c
index ab25d142..e1fbc09f 100644
--- a/src/tunnel.c
+++ b/src/tunnel.c
@@ -28,6 +28,7 @@
 #include <string.h>
 #include <strings.h>
 #include <unistd.h>
+#include <getopt.h>
 
 #ifndef __MINGW32__
 #include <errno.h>
@@ -696,16 +697,30 @@ int main(int argc, char **argv)
     ss_addr_t tunnel_addr = { .host = NULL, .port = NULL };
     char *tunnel_addr_str = NULL;
 
+    int option_index                    = 0;
+    static struct option long_options[] = {
+        { "help", no_argument, 0, 0 },
+        {      0,           0, 0, 0 }
+    };
+
     opterr = 0;
 
     USE_TTY();
 
 #ifdef ANDROID
-    while ((c = getopt(argc, argv, "f:s:p:l:k:t:m:i:c:b:L:a:n:P:uUvVA")) != -1) {
+    while ((c = getopt_long(argc, argv, "f:s:p:l:k:t:m:i:c:b:L:a:n:P:huUvVA",
+                            long_options, &option_index)) != -1) {
 #else
-    while ((c = getopt(argc, argv, "f:s:p:l:k:t:m:i:c:b:L:a:n:uUvA")) != -1) {
+    while ((c = getopt_long(argc, argv, "f:s:p:l:k:t:m:i:c:b:L:a:n:huUvA",
+                            long_options, &option_index)) != -1) {
 #endif
         switch (c) {
+        case 0:
+            if (option_index == 0) {
+                usage();
+                exit(EXIT_SUCCESS);
+            }
+            break;
         case 's':
             if (remote_num < MAX_REMOTE_NUM) {
                 remote_addr[remote_num].host   = optarg;
@@ -760,6 +775,9 @@ int main(int argc, char **argv)
         case 'v':
             verbose = 1;
             break;
+        case 'h':
+            usage();
+            exit(EXIT_SUCCESS);
         case 'A':
             auth = 1;
             break;
@@ -771,6 +789,10 @@ int main(int argc, char **argv)
             prefix = optarg;
             break;
 #endif
+        case '?':
+            // The option character is not recognized.
+            opterr = 1;
+            break;
         }
     }
 
diff --git a/src/utils.c b/src/utils.c
index cff3c6c7..245f12d9 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -205,7 +205,7 @@ void usage()
 #endif
     printf("\n");
     printf(
-        "       -s <server_host>           Host name or ip address of your remote server.\n");
+        "       -s <server_host>           Host name or IP address of your remote server.\n");
     printf(
         "       -p <server_port>           Port number of your remote server.\n");
     printf(
@@ -219,9 +219,13 @@ void usage()
     printf(
         "                                  bf-cfb, camellia-128-cfb, camellia-192-cfb,\n");
     printf(
-        "                                  camellia-256-cfb, cast5-cfb, des-cfb, idea-cfb,\n");
+        "                                  camellia-256-cfb, cast5-cfb, des-cfb,\n");
     printf(
-        "                                  rc2-cfb, seed-cfb, salsa20 and chacha20.\n");
+        "                                  idea-cfb, rc2-cfb, seed-cfb, salsa20 and\n");
+    printf(
+        "                                  chacha20.\n");
+    printf(
+        "                                  The default cipher is tables.\n");
     printf("\n");
     printf(
         "       [-a <user>]                Run as another user.\n");
@@ -289,7 +293,9 @@ void usage()
 #endif
     printf("\n");
     printf(
-        "       [-v]                       Verbose mode\n");
+        "       [-v]                       Verbose mode.\n");
+    printf(
+        "       [-h, --help]               Print this message.\n");
     printf("\n");
 }