The demodulation precision of multi-channel grating sensing demodulation system is directly related to the degree of signal synchronization. In order to ensure the demodulation effect, the signal synchronization method of multi-channel grating sensing demodulation system is studied. Based on the application principle of multi-channel grating sensing demodulation system, it is determined that the transmission delay of adjacent gratings in the process of demodulation leads to overlapping of reflected optical signals and cannot guarantee the synchronization of multi-channel signals. After fully analyzing the signal delay of the demodulation system, Kalman filter method is used to complete the phase deviation compensation according to the frequency deviation compensation, and realize the multi-channel synchronous time compensation, so as to complete the signal synchronization of the multi-channel grating sensor demodulation system. The test results show that the time synchronization deviation is lower than 0.15 ms after the signal synchronization of multi-channel grating sensing demodulation system is carried out by the research method. The bit error rate of demodulation system after signal synchronization is lower than 0.55%. The maximum drift after demodulation is 0.007 8 nm. It can effectively avoid overlapping of reflected light signals.