In recent years, along with the transformation and restructuring of the power industry, the generation side market power problem has become the focus in the process of electricity market reform in various countries. On the basis of sufficient research, this paper summarizes and comprehensively reviews the basic concept of market power, common market power monitoring indicators, market power mitigation methodologies, and introduces the implementation status of typical power markets in the United States, the United Kingdom, and Nord Pool. The purpose of this paper is to provide a research basis and referential ideas for market power monitoring and mitigation mechanisms establishment in China, further lead to effective prevention of market power, to ensure the effectiveness and fairness of market competition, to realize standardized management of market participants, and to improve the market operation efficiency.