Space laser communication system has the characteristics of high transmission rate, small volume, light weight and low power consumption, which is suitable for satellite high-speed data transmission. As key technology of space laser communication system, laser modulation is one of the main factors affecting its communication performance. This article first introduces the principle and classification of various space laser communication modulation techniques, and makes a comparative analysis of their advantages and disadvantages, and then elaborates the key technologies of laser modulation. Finally, from the perspective of development stage and application environment, the research progress of the existing reported space laser communication modulation technology at home and abroad is summarized, and the development trend of space laser communication modulation technology is prospected.