Abstract: Abstract: Distributed photovoltaic power generation system has intermittency and fluctuation, and there is a harmonic source represented by power electronic equipment in the system. After it is connected to the coal mine distribution network, it will have many adverse effects on the power supply quality.This paper expounds the positioning of distributed photovoltaic power generation system, and defines its operation mode after being connected to coal mine distribution network. From the changes after the distributed photovoltaic power generation system is connected to the coal mine distribution network, its impact on the coal mine distribution network is analyzed. It is obtained that the change of power flow distribution, the fluctuation of photovoltaic power and the injection of harmonic source are the main factors of adverse effects, as well as the boundary conditions of adverse effects. Based on the analysis of the characteristics of coal mine distribution network, the grid connection design principle of using distribution network load and minimum three-phase short-circuit current to limit the adverse effects is summarized.