The initial reliability assessment of distribution systems was based on the classical method of reliability assessment for engineering systems. In the mid-twentieth century, reliability evaluation methods in the field of distribution systems had extensive development, and some approximate methods for calculating the outage rate and outage time of distribution systems were proposed. The proposal of these methods provided conditions for the formation of a reliability evaluation method system for distribution systems in the future. Distributed power supply devices refer to small modular, environmentally compatible independent power sources with power ranging from several kilowatts to 50 MW. These power sources are owned by the power sector, power users, or third parties to meet the specific requirements of the power system and users. Such as peak shaving, supplying power to remote users or commercial and residential areas, saving investment in power transmission and transformation, improving power supply reliability, and so on. This article mainly focuses on the reliability research of active distribution microgrids containing distributed power sources. Firstly, relevant research is summarized, relevant application methods are proposed, and the results are discussed.