Abstract: A typical flow for SIP message exchange is studied, reasons that cause performance degradation are mainly analyzed, and an optimized algorithm that randomly makes the decision of acceptance or rejection of every packet is proposed for overload control of SIP signaling network. The algorithm is verified and analyzed with simulation, and the results show that this solution can restrain throughput jitter, lower service refuse rate, reduce buffer queue length, shorten call setup time and better meet the demand on SIP signaling network under heavy load.