Abstract: The devices which need time synchronization are numerous and distributed broadly in nuclear power station, and there are different requirements of precision and mode among different devices. Therefore several time synchronizing systems exist in nuclear power station at present. The modes of time adjustment, precision and transmission channel are discussed in this paper, and in order to solute the problem which time synchronizing systems are not unified and mounted repeatedly, a optimal time synchronizing network is presented which has unique time source. This time synchronizing system has high availability and precision because of its main clock and GPS/China compass dual-mode satellite antenna. The main clock and sub-clock is connected through optical fiber and transmission delay is set to improve system precision. Analysis result indicates that the optimal time synchronizing network has higher reliability and precision, and it also realize the optimization of technology and economy.