Abstract: In order to effectively suppress the impact factors of space laser communication performance, such as atmospheric disturbances and so on. An atmospheric laser communication system was described that took a new modulation method that was Circle Polarization Shift Keying(CPolSK). The working principle was introduced. The system model of CPolSK was given, and the factors that affeced the performance of communication in the system were analyzed. The four parameters of the detector noise, the sensitivity, the atmospheric channel attenuation and the transmission power which impacted on communication performance were considered. The experimental study of polarization shift keying system communication process was done by the OptiSystem software. The results indicate that the communication performance of the based CPolSK atmospheric laser communication system is obvious better than OOK system under identical communication conditions.