With the enlarging application field of the space-borne SAR system, its requirement becomes more and more complicated.Hence, it is more important to develop a low budget light-SAR for specified need. In this paper, the development of spaceborne light-SAR for small satellite is summarized based on the development status of spaceborne SAR and representative light-SAR, including balanced development strategy, low complexity load, modular rapid response system and satellite networking, multi-system parallel technology route, et al. Combined with typical light SAR systems, the key techniques, character, application and performances of different systems are analyzed and compared.