GB/T 28181 standards formulate information transmission, switching,control technology requirements of security video surveillance network system, as an application server, the signaling security gateway is responsible for receiving or forwarding the SIP signaling between domains, adding identification and authentication. This paper analyzes the basic functional requirements of signaling security gateway, proposes design of security module. It achieves authentication, confidentiality and integrity of information by encrypting, decrypting the forwarding signaling and digital signature. This design has better performance and stability through the actual running.