The invention relates to a synchronization device and a method of a direct-current transmission control protection system based on TDM (time division modulation). The device and the method realize the synchronization of the system through adopting high speed performance and real-time performance of a TDM bus. The realization device comprises a measuring system and a control system, wherein TDM bus interfaces are integrated on each acquisition board card in the measuring system; each of the acquisition board card is connected mutually through TDM; the control system comprises a TDM bus board card and a control unit; and the measuring system is connected with the control system through the TDM bus. The acquisition system is also provided with a frequency following module so as to ensure that the sampling numbers of the acquisition system in each work frequency period keep the same. The realization method is that the ideal synchronous sampling of each acquisition board card in the measuring system can be guaranteed through a synchronous head of a TDM frame and a certain delay. With the adoption of the device and the method, the data synchronization between the measuring system and the control system in the direct-current transmission control protection system can be realized.