Abstract: Distributed power access brings a lot of impact to the entire power grid, especially to the distribution network related with it directly, such as power flow, power quality, power distribution reliability and so on. Distributed power access to the distribution network changes the radiation mode with single power supply into network mode with multi-power supply, the operation mode is complicated, Therefore, the traditional reliability assessment method is no longer applicable; need further study of new methods. Firstly, the influence of distributed power access on the traditional reliability algorithm is studied in this paper，and establishes the Isolated island partitioning model and Isolated island partitioning process, and makes Dynamic solution. Based on the existing assessment methods, this paper presents a method of distribution network reliability assessment based on load and power stochastic functions according to different characteristics of distributed power supply and traditional power supply, and the actual example shows that the distribution Power supply can improve the reliability index of distribution network and improve user's power quality.