diff --git a/listener/sing_tun/server.go b/listener/sing_tun/server.go
index 2dc6524e..b1be5dfb 100644
--- a/listener/sing_tun/server.go
+++ b/listener/sing_tun/server.go
@@ -59,12 +59,14 @@ func CalculateInterfaceName(name string) (tunName string) {
 	if err != nil {
 		return
 	}
-	var tunIndex int
+	var tunIndex int = 0
 	for _, netInterface := range interfaces {
 		if strings.HasPrefix(netInterface.Name, tunName) {
 			index, parseErr := strconv.ParseInt(netInterface.Name[len(tunName):], 10, 16)
 			if parseErr == nil {
-				tunIndex = int(index) + 1
+				if int(index)+1 > tunIndex {
+					tunIndex = int(index) + 1
+				}
 			}
 		}
 	}