diff --git a/wxpay.go b/wxpay.go
index 5f50f72..013a59e 100644
--- a/wxpay.go
+++ b/wxpay.go
@@ -3,6 +3,7 @@ package pay
 import (
 	"context"
 	"errors"
+	"fmt"
 	"git.oa00.com/go/rsa"
 	"github.com/wechatpay-apiv3/wechatpay-go/core"
 	"github.com/wechatpay-apiv3/wechatpay-go/core/auth/verifiers"
@@ -38,7 +39,7 @@ func InitWxpay(config WxpayConfig) error {
 	}
 	// 使用商户私钥等初始化 client，并使它具有自动定时获取微信支付平台证书的能力
 	opts := []core.ClientOption{
-		option.WithWechatPayAutoAuthCipher(config.MchID, certificate.SerialNumber.String(), privateKey, config.MchAPIv3Key),
+		option.WithWechatPayAutoAuthCipher(config.MchID, fmt.Sprintf("%x", certificate.SerialNumber), privateKey, config.MchAPIv3Key),
 	}
 	Wxpay.Client, err = core.NewClient(context.Background(), opts...)
 	if err != nil {