The invention relates to an MMC-HVDC direct-current short-circuit fault ride-through method based on the direct-current bus bipolar equipotential, and belongs to a direct-current fault protection method of a flexible direct-current power transmission system. According to the method, the double-pole potential of the MMC direct-current side bus is controlled to be approximately equal, so that the short-circuit fault current of the direct-current side is close to zero, and the direct-current bipolar short-circuit fault ride-through can be realized under the condition that the MMC is controllable. The basic principle is that after the direct-current short-circuit current is detected, a fault operation mode is adopted, and on and off states of upper and lower three-phase bridge arms of the MMC three-phase are selected according to the polarity of the power grid voltage, the MMC circuit topology is equivalent to the chain type star topology, and the three-phase conducted upper and lower bridge arm voltage is controlled to withstand the voltage of the power grid, and the double-pole electric potential of the direct-current bus is approximately equal, the direct-current side short-circuit fault current is close to zero. An alternating-current circuit breaker is not needed, and the capacitor voltage balance of the MMC sub-module is maintained during the fault ride-through period, and after the fault is eliminated, the power transmission can be rapidly restored.