diff --git a/lib/qiniu/auth.rb b/lib/qiniu/auth.rb
index b552d62..c880d07 100755
--- a/lib/qiniu/auth.rb
+++ b/lib/qiniu/auth.rb
@@ -176,6 +176,7 @@ module Qiniu
           return "#{download_url}&token=#{dntoken}"
         end # authorize_download_url
 
+        ### 对包含中文或其它 utf-8 字符的 Key 做下载授权
         def authorize_download_url_2(domain, key, args = EMPTY_ARGS)
           url_encoded_key = CGI::escape(key)