Abstract: ±200 MVar STATCOM is by far the largest-capacity dynamic reactive power compensation device in the world. Because of the voltage-supporting function and higher cost, it is necessary to discuss protection strategies of commutation devices and auxiliary equipment; and then, to make it safety and reliable. In this paper, on the basic of analyzing main circuit design and H-bridge structure of cascaded STATCOM, select and discuss several aspects of relay-protection including device-level protection strategies of STATCOM, module-level protection strategies of STATCOM, breaker malfunction protection strategies; finally propose optimizations for protection scheme. A Clearer protection configuration and optimization strategies have a greater significance for multi-H-bridge cascade STATCOM in engineering applications.