The embodiments of the present invention provide a data synchronization method and device. The method comprises the following steps that: after the fault of any one control station is restored, output locking is performed on a malfunctioned control station in the distributed control system of a nuclear power plant, so that the malfunctioned control station can be in a bypass state; the variables of the malfunctioned control station are compared with the variables of a functioned control station, so that data to be synchronized are determined; and a data transmission channel with the malfunctioned control station is established, data synchronization is performed on the data to be synchronized based on the established data transmission channel. With the data synchronization method and device provided by the embodiments of the present invention adopted, data can be reliably and accurately synchronized to the malfunctioned control station, operation is simple, and the security and usability of the distributed control system are ensured.