diff --git a/weixin-java-miniapp/src/main/java/cn/binarywang/wx/miniapp/bean/xpay/WxMaXPaySigParams.java b/weixin-java-miniapp/src/main/java/cn/binarywang/wx/miniapp/bean/xpay/WxMaXPaySigParams.java
index 089f2d5390e579121227017c6f6bf4a41d0953f0..3e11c83b2c8bd6213371b6eb38ec217bdc198426 100644
--- a/weixin-java-miniapp/src/main/java/cn/binarywang/wx/miniapp/bean/xpay/WxMaXPaySigParams.java
+++ b/weixin-java-miniapp/src/main/java/cn/binarywang/wx/miniapp/bean/xpay/WxMaXPaySigParams.java
@@ -52,7 +52,7 @@ public class WxMaXPaySigParams implements Serializable {
     String ak = StringUtils.trimToEmpty(this.appKey);
     final String sigUri = convUrlToSigUri(url);
     final String paySig = calcPaySignature(sigUri, postBody, ak);
-    return paySig;
+    return paySig.toLowerCase();
   }
 
   public String calcSig(String postBody) {