Abstract: To fully demonstrate the view that polarization modulation can effectively suppress the influence of atmospheric turbulence，this paper analyzes polarization shift keying and several kinds of intensity modulation which are widely used in atmospheric laser communication systems. The comparative study of various modulation modes contains of power utilization, bandwidth requirement, transmission capacity and error performance. The results show that PolSK is more superior to any other kinds of intensity modulation mode when we consider all aspects of the performance. It has the maximum transmission capacity, the smallest bandwidth and receiving bit error rate. Thus, the polarization modulation is more suitable to be used in atmospheric laser communication.