Abstract: This paper mainly discusses the principle of rooftop photovoltaic power supply access to the distribution network and analyzes the distribution network fault protection after photovoltaic connection, on this basis, the simulation experiment is carried out. The results show that after access, a certain fault current will be provided, after photovoltaic connection,and the original protection sensitivity of the distribution network will change accordingly, so the protection value must be adjusted according to the simulation results. The whole county rooftop photovoltaic demonstration, mainly access to medium voltage (special transformer), low voltage (public transformer). This paper analyzes the protection configuration of the distribution area after the small capacity photovoltaic power is connected to the low voltage.