To solve the DC side voltage balancing problem of MMC-SVG under single phase, this paper first explained the operating principles of Modular Multilevel Converter (MMC). By building the math models of MMC, the paper analyzed the reason of generating current which flowed through MMC. Based on that conclusion, this paper proposed a voltage balancing method and a voltage averaging method to maintain the voltage of every capacitor. In addition, the paper presented a faster reactive current detecting method to realize the MMC-STATCOM. Finally, the Matlab/Simulink simulation indicated these control methods are reliable.