The invention provides an overvoltage protective device and an overvoltage protective method applicable to wind power hydrogen production and energy storage system grid connection. The overvoltage protective device comprises a detecting and processing unit, a multistage serial conversion unit, a grid-connected inverter unit, a stored hydrogen energy conversion unit, a wind power converter and an overvoltage protective unit. The overvoltage protective method includes collecting voltage on a direct-current side of the wind power converter through the wind power detection unit, controlling a connection sequence of IGBTs of the multistage serial conversion unit through an IR drive unit, and generating power and conducting grid connection by the stored hydrogen energy conversion unit; sending acontrol signal through a microprocessor unit, blocking input signals of a voltage detection unit, connecting IGBTs of the overvoltage protective unit, connecting the stored hydrogen energy conversionunit into the overvoltage protective unit, and switching off the IGBTs of the multistage serial conversion unit. The overvoltage protective device and the overvoltage protective method have the advantages that voltage change on the direct-current side of the converter can be detected in real time and effective overvoltage protection of the direct-current side of the converter can be achieved through stored hydrogen energy, so that an intelligent protection function is achieved.