Improving the MMC - structure of STATCOM can make its have DC output ability and achieve the function of high voltage power grid DC ice-melting. Modular multi-level converter has a common DC side and energy can flow to each other between each MMC phase, with which four-quadrant operation is achieved, and it adopts modular design, which is very suitable for high-pressure and high-power situations. The power sub-module switching device, which takes new high power and low driving power turn-off devices Injection Enhanced Gate Transistor, can expand the capacity of the device and achieve high current DC ice-melting and high power compensation. Static Synchronous Compensator (STATCOM) also provides a more accurate and efficient ability to compensate for reactive power compensation. Three-phase MMC-STATCOM simulation models are built in the Matlab software, the theoretical analysis is verified by simulation that the proposed structure can be stable and run faster in the grid.