In order to solve the problem of pre-acceleration auto reclosing is coincident with the permanent fault when the photovoltaic system is connected to the distribution network, a new method is proposed for permanent fault diagnosis of three phase auto reclosing for photovoltaic power distribution network. This method takes the transient fault model as reference, the mathematical model of linear model of line fault is established, the least square algorithm is used to identify the line phase capacitance, a permanent fault identification criterion is established based on the identification error of the phase to phase capacitance. The recognition value is close to the actual value when the line is transient fault; the difference between the recognition value and the real value is larger and when the line is permanent fault. A simulation model is established by using the PSCAD, the transient fault and permanent fault are simulated for the grid connected photovoltaic system. Simulation results show that the proposed method can identify the fault types of the grid connected PV system, and the correctness and validity of the method is verified. This work is supported by National Natural Science Foundation of China (No. 51367017).