Abstract: Facing with the lack of security in current running client/server systems, this paper designs and implements a kind of secure tunnel gateway system based on SSL/TLS protocol in order to provide seamless security integration to them.Client tunnel gateway and server tunnel gateway authenticate each other based on X.509 certificate, and create SSL/TLS connections to transmit the clients′ requests and servers′ responses.The gateway system uses normal TCP/IP connections to transport data with the clients and servers.It provides confidentiality, integrity and authentication for clients/servers data transmission, which needs no modification to them.Then, this paper presents its test result and application instances.