In the Mobile Internet era, many Instant Messaging applications such as WeChat, Ali DingTalk, YiXin and other similar applications have emerged. How to serve for Instant Messaging applications effectively in the current system is a problem to be considered. Session Initiation Protocol is a signaling protocol in application layer. It has advantages in dealing with session, but inadequate in dealing with instant message. This paper describes the design and implementation of a new SIP server system based on the research and analysis of SIP which can deal with instant message better. In addition, SIP Broker can be deployed through the cluster, which can provide supports for future services expansion.