diff --git a/docs/usage.md b/docs/usage.md
index 132862b4..4a31c3ec 100644
--- a/docs/usage.md
+++ b/docs/usage.md
@@ -27,6 +27,6 @@ Here, we will present a list of things you should do before you start a trojan s
 - Apply for or self-sign (**NOT RECOMMENDED**) an `SSL` certificate.
 - Correctly write the [config file](config).
 
-[Shadowsocks SIP003](https://shadowsocks.org/en/spec/Plugin.html) is supported by trojan, but it is added as an experimental feature and is not standard at all, so it will not be documented here.
+[Shadowsocks SIP003](https://shadowsocks.org/doc/sip003.html) is supported by trojan, but it is added as an experimental feature and is not standard at all, so it will not be documented here.
 
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