According to the engineering conditions and requirements of 20 MW photovoltaic power generation system, the mode of block power generation and centralized grid connection is used in the overall scheme of the system. The 260 W polysilicon solar modules is chosen, the fixed installation method is adopted in operation mode of photovoltaic array, and the inclined angle of photovoltaic array is 23°, 500 kW grid connected inverters are put to use, and distance between the North and South is 5.2 m in photovoltaic arrays. The design of access power system, main electrical connection and electric equipment configuration are carried out in electric primary system. The calculation results show that annual average on-grid energy is 17 954 MW·h, annual utilization hour of equivalent full load is 896.4 h, capacity coefficient is 0.102, and the energy-saving and environmental benefit are well.