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Through the analysis of the present stage punctual system's practical application situation and technical characteristic, to propose a new designing program of the time keeping system and design a time keeping system based on FPGA and the finite state machine. Using the oven controlled crystal oscillator as the local clock and the input signals of the system together with GPS/beidou. FPGA is used to design the basic circuit and the finite state machine of the time keeping system and to control the two parts of frequency modulation and phase modulation and the external D/A converter circuit, then achieves local clock with the clock source to output the same frequency and phase completely,thus obtains the high accuracy time base quickly. It can keep the clock source signal after GPS/beidou loses lock to achieve time synchronization of the communication system.