A direct current voltage control method, applied to a multi-terminal DC transmission system, wherein the multi-terminal DC transmission system comprises a DC voltage primary control station and at least one DC voltage secondary control station, and the method comprises: determining, when it is determined that the DC voltage primary control station loses a DC voltage control function, whether the DC voltage primary control station can communicate with the DC voltage secondary control station, and if yes, sending, by the DC voltage primary control station, information about the DC voltage primary control station losing the DC voltage control function to the at least one DC voltage secondary control station and enabling a DC voltage control function of one of the at least one DC voltage secondary control station, so as to adjust the DC voltage; before the DC voltage control function of the one of the at least one DC voltage secondary control station is enabled, if the DC voltage exceeds an operation range, enabling, by the at least one DC voltage secondary control station, a DC voltage auxiliary control function, so as to adjust emitted or absorbed active power; and when the DC voltage primary control station cannot communicate with all of or some of the at least one DC voltage secondary control station, and if the DC voltage exceeds the operation range, enabling, by the at least one DC voltage secondary control station, a DC voltage auxiliary control function, so as to adjust current emitted or absorbed active power, and determining, according to a policy, one DC voltage secondary control station to enable a DC voltage control function, so as to adjust the DC voltage; characterized in that after the enabling, by the at least one DC voltage secondary control station, a DC voltage auxiliary control function, the method further comprises: counting, by the DC voltage secondary control station that has the DC voltage auxiliary control function enabled, times of enabling the DC voltage auxiliary control function, and determining, when a counted quantity exceeds a respective set threshold, one DC voltage secondary control station to enable a DC voltage control function, so as to adjust the DC voltage. determining, when it is determined that the DC voltage primary control station loses a DC voltage control function, whether the DC voltage primary control station can communicate with the DC voltage secondary control station, and if yes, sending, by the DC voltage primary control station, information about the DC voltage primary control station losing the DC voltage control function to the at least one DC voltage secondary control station and enabling a DC voltage control function of one of the at least one DC voltage secondary control station, so as to adjust the DC voltage; before the DC voltage control function of the one of the at least one DC voltage secondary control station is enabled, if the DC voltage exceeds an operation range, enabling, by the at least one DC voltage secondary control station, a DC voltage auxiliary control function, so as to adjust emitted or absorbed active power; and when the DC voltage primary control station cannot communicate with all of or some of the at least one DC voltage secondary control station, and if the DC voltage exceeds the operation range, enabling, by the at least one DC voltage secondary control station, a DC voltage auxiliary control function, so as to adjust current emitted or absorbed active power, and determining, according to a policy, one DC voltage secondary control station to enable a DC voltage control function, so as to adjust the DC voltage; characterized in that after the enabling, by the at least one DC voltage secondary control station, a DC voltage auxiliary control function, the method further comprises: counting, by the DC voltage secondary control station that has the DC voltage auxiliary control function enabled, times of enabling the DC voltage auxiliary control function, and determining, when a counted quantity exceeds a respective set threshold, one DC voltage secondary control station to enable a DC voltage control function, so as to adjust the DC voltage.