Aiming at the fault of pole-to-pole situation in the DC side of MMC,the fault current circuit of the MMC is established and the current distribution and junction temperature calculation of the diode and protective thyristor in the MMC are given for evaluating bipolar DC short circuit fault tolerance.The model and simulation of the fault current loop of the MMC is carried out under MATLAB/Simulink,and the experiment is carried out in the MMC back-to-back test system.Simulation and experimental results show that the proposed method is accurate and effective.The proposed method has important theoretical significance for checking the tolerance of pole-to-pole short-circuit fault and device selection in practical engineering in MMC.