diff --git a/utils.js b/utils.js
index 21b311b..42e7f4a 100644
--- a/utils.js
+++ b/utils.js
@@ -335,6 +335,19 @@ function safeDumpErrStack(err) {
   }
 }
 
+function normalMd5UrlSign(params, $secretKey) {
+  const sortedKeys = params.keys().sort();
+  const connStr = '&';
+  let paramsStr = '';
+  sortedKeys.forEach
+  (
+    (key) => {
+      paramsStr += '' + key + '=' + params[key] + connStr;
+    }
+  );
+  return md5Str(paramsStr + $secretKey);
+}
+
 exports.rspErr = rspErr;
 exports.rspOk = rspOk;
 exports.rspData = rspData;
@@ -377,3 +390,4 @@ exports.mapToObject = mapToObject;
 exports.arrayToStrings = arrayToStrings;
 exports.removeLeadZero = removeLeadZero;
 exports.safeDumpErrStack = safeDumpErrStack;
+exports.normalMd5UrlSign = normalMd5UrlSign;