diff --git a/neutrino-proxy-server/src/main/java/fun/asgc/neutrino/proxy/server/service/PortMappingService.java b/neutrino-proxy-server/src/main/java/fun/asgc/neutrino/proxy/server/service/PortMappingService.java
index fd9843f3..0aa5e03e 100644
--- a/neutrino-proxy-server/src/main/java/fun/asgc/neutrino/proxy/server/service/PortMappingService.java
+++ b/neutrino-proxy-server/src/main/java/fun/asgc/neutrino/proxy/server/service/PortMappingService.java
@@ -107,7 +107,7 @@ public class PortMappingService {
 		}
 		PortPoolDO portPoolDO = portPoolMapper.findByPort(req.getServerPort());
 		ParamCheckUtil.checkNotNull(portPoolDO, ExceptionConstant.PORT_NOT_EXIST);
-		ParamCheckUtil.checkNotNull(portMappingMapper.findByPort(req.getServerPort()), ExceptionConstant.PORT_CANNOT_REPEAT_MAPPING, req.getServerPort());
+		ParamCheckUtil.checkExpression(null == portMappingMapper.findByPort(req.getServerPort()), ExceptionConstant.PORT_CANNOT_REPEAT_MAPPING, req.getServerPort());
 
 
 		Date now = new Date();