diff --git a/README.md b/README.md
index 1a1bb5b..18dd0d0 100644
--- a/README.md
+++ b/README.md
@@ -31,6 +31,9 @@ Usage of ./gomysql2struct:
   -h	help message
   -key string
     	eth address private key
+  -limit uint
+    	gas limit of tx
+    	default is 0, when limit is 0, it will keep the old gas limit in the original tx
   -swap string
     	rpc uri of eth
   -txid string
diff --git a/cmd/main.go b/cmd/main.go
index 0689d72..8b56e48 100644
--- a/cmd/main.go
+++ b/cmd/main.go
@@ -165,6 +165,7 @@ func main() {
 	var sourceKey = flag.String("key", "", "eth address private key")
 	var oldTxID = flag.String("txid", "", "txid to speed up")
 	var gas = flag.Int64("gas", 10, "gas price value in gwei")
+	var newGasLimit = flag.Uint64("limit", 0, "gas limit of tx\ndefault is 0, when limit is 0, it will keep the old gas limit in the original tx")
 	var h = flag.Bool("h", false, "help message")
 	flag.Parse()
 	if *h {
@@ -194,10 +195,13 @@ func main() {
 			log.Fatalf("input decode err: %s", err.Error())
 		}
 	}
-	gasLimit, err := hexutil.DecodeBig(rpcTx.Gas)
+	gasLimit, err := hexutil.DecodeUint64(rpcTx.Gas)
 	if err != nil {
 		log.Fatalf("error gas limit: %s", rpcTx.Gas)
 	}
+	if gasLimit < *newGasLimit {
+		gasLimit = *newGasLimit
+	}
 	nonce, err := hexutil.DecodeUint64(rpcTx.Nonce)
 	if err != nil {
 		log.Fatalf("error nonce: %s", rpcTx.Nonce)
@@ -216,7 +220,7 @@ func main() {
 		nonce,
 		common.HexToAddress(rpcTx.To),
 		value,
-		uint64(gasLimit.Int64()),
+		gasLimit,
 		gasPrice,
 		inputBs,
 	)