The invention discloses a grid fault ride-through control method for a flexible direct-current transmission system. Grid fault non-communication ride-through of the system is achieved by switching converter station control modes, direct-current side voltage is detected in real time to judge whether a grid breaks down or not, control module switching is carried out, grid fault ride-through is achieved, and a controller supporting grid fault non-communication ride-through of the flexible direct-current transmission system is formed. By optimizing an original controller with the control method, direct-current voltage is effectively controlled in a grid fault of a constant direct-current voltage side converter station when no communication exists between converter stations under the condition that no hardware circuit is additionally arranged, the converter stations still keep operating during the grid fault, and meanwhile the system can be restored to an operating state before the fault as soon as possible after the fault is removed; grid fault non-communication ride-through of the flexible direct-current transmission system is achieved on the whole, the alternating-current fault ride-through capability of flexible direct-current transmission is improved, and a good operating environment is provided for the safety and stability of the system.