The invention provides a control method for reducing the probability of direct current transmission commutation failure. A unified power flow controller is installed at an alternating current station adjacent to a direct current transmission system inverter station, and the unified power flow controller and a direct current transmission system are connected to the same alternating current system. By means of the above structure, after the alternating current voltage of the direct current transmission system inverter station is detected to decrease, the control mode of the unified power flow controller is quickly switched to an injection voltage control mode, and the voltage of the access bus of the unified power flow controller is controlled and increased, thus increasing the voltage of the access alternating current bus of the direct current transmission system inverter station and reducing the probability of commutation failure of the direct current transmission system. Compared with other reactive power compensation and voltage control devices, the structure is more economical, and the control method has a more significant effect on reducing the probability of direct current transmission commutation failure.