As one of the most serious faults of the modular multilevel converter HVDC system, the dc side bipolar short circuit will lead to serious overcurrent of the converter bridge arm and threaten the safety of the system.In order to suppress the overcurrent, a method of using bridge arm reactor coupling to suppress the fault overcurrent is proposed.Suppress short-circuit current by coupling the reactors of the upper arm and lower arm in the same phase of the modular multilevel converter.The method is evaluated objectively from three aspects through simulation.The results show that the proposed method can effectively reduce the loss and inhibit the increase of fault current in bipolar fault, thus gaining time for protection.