diff --git a/bcutils.js b/bcutils.js
index 7907ee9..187caa1 100644
--- a/bcutils.js
+++ b/bcutils.js
@@ -120,7 +120,7 @@ function extractSubParams(param) {
   } else if (param.toString().length > 40) {
     throw 'extractSubparams error to long:' + param;
   } else {
-    subParams[0] = param.toString().substr(0, param.toString().length - 20);
+    subParams[0] = param.toString().substr(0, 10);
     subParams[1] = param.toString().substr(10);
   }
   subParams[0] = utils.removeLeadZero(subParams[0]);