diff --git a/websocket-sharp/Net/HttpListenerRequest.cs b/websocket-sharp/Net/HttpListenerRequest.cs
index 701128120..60162a303 100644
--- a/websocket-sharp/Net/HttpListenerRequest.cs
+++ b/websocket-sharp/Net/HttpListenerRequest.cs
@@ -343,8 +343,10 @@ public Version ProtocolVersion {
     /// </value>
     public NameValueCollection QueryString {
       get {
+        //fix bug, if ContentEncoding is GB2312 ,UrlDecode will return ??? 
+        //TODO,how to get paratermers when method is POST
         return _queryString ??
-               (_queryString = HttpUtility.InternalParseQueryString (_url.Query, Encoding.UTF8));
+               (_queryString = HttpUtility.InternalParseQueryString (_url.Query,this.ContentEncoding));
       }
     }