Session initiation protocol(SIP) has been chosen as the call/session control protocol in IP multimedia subsystem(IMS). However, large SIP messages create a bottleneck for SIP application in IP multimedia subsystem(IMS) in wireless applications. Based on the SigComp, and by comparing various compression algorithms, lempel ziv storer szymanski(LZSS) is selected as the basic algorithm to compress SIP in accordance with the characteristics of messages in SIP protocol. To further improve the compression ratio, a new algorithm is proposed based on LZSS and Huffman. The performance of the compression algorithm is analyzed via simulation.