The multi-microgrid system plays a crucial role in the future energy Internet as it effectively addresses the grid fluctuations caused by renewable energy. The smooth operation of a multi-microgrid system hinges on efficient energy scheduling between the microgrids. Based on the research of multi-microgrid optimization scheduling at domestic and overseas, this paper divides the multi-microgrid optimization scheduling into three aspects: uncertainty optimization scheduling, multi-microgrid optimization scheduling considering demand response, and hierarchical optimization scheduling of distribution network and multi-microgrid. The existing research results are analyzed, compared and summarized in detail from these three aspects, hoping to provide future research directions for scholars.