The invention relates to a wind power fault ride-through method and device of a flexible DC grid and a controller thereof. The method comprises a step of determining an output of a wind power base tobe adjusted according to transmission power before and after a fault of a flexible DC grid, a step of determining a change value of converter station output to an AC grid frequency according to the output of the wind power base to be adjusted, and a step of determining an output power adjustment amount of a wind turbine according to the change value of the converter station output to the AC grid frequency and adjusting the output power of the wind turbine by using the output power adjustment amount of the wind turbine. According to the technical scheme provided by the invention, a power emergency control strategy for connecting a wind turbine island to a flexible grid is provided, after a flexible grid fault occurs, the converter station changes the frequency of an AC side according to a power control requirement, and the wind turbine responds to the frequency to control the power in time to achieve fault ride-through.