Abstract: In order to assess the risk of continuous commutation failure in the DC transmission system caused by the chain of the wind turbine off-grid, a method based on electrical distance is proposed to establish a fault set that causes the DC system to exit from operation after the wind turbines tripped off from the grid. In this method, according to the fan off-grid index, the risk indicator (RI) that indicates the fault-induced wind turbine off-grid is introduced; the RI is characterized by calculating the electrical distance between the fault point and the wind farm, and the fault is filtered and sorted according to the size of the RI value; Furthermore, in the PSASP transient calculation, the fault set is constructed by screening the accident sequence that causes the system fan to escape the net. Finally, the simulation of CEPRI36v7 AC/DC hybrid system is calculated by PSASP to verify the effectiveness of the proposed method.