In order to avoid the large errors in calculating the fiber Bragg grating (FBG) center wavelength caused by the unstable modulation depth when the phase generated carrier (PGC) demodulation method is used to demodulate the signals of FBG vibration sensors,a PGC-arctangent-peak finding (PGC-Arctan-PF) joint demodulation algorithm is proposed .Firstly,the output signal of the optical path multiplied with the fundamental frequency and the two-fold frequency of the carrier signal respectively.Then passing them through the low-pass filter (LPF) to obtain quadrature signals of different amplitude containing the vibration information to be measured.After that,the peaks of this orthogonal signal are searched one by one.The average amplitude of the two signals is calculated separately.The average amplitude is cross multiplied of the two signals to make the quadrature signals equal in amplitude.Finally,the frequency and amplitude of the stretched FBG are accurately solved after an arctangent operation and high-pass filter (HPF) processing.The feasibility of the PGC-arctan-PF algorithm is verified by simulation and experiment.This algorithm can accurately solve the vibration signal from 100 Hz to 1 000 Hz,and the relative error of FBG wavelength calculation is less than 0.81%.The PGC-Arctan-PF algorithm can effectively avoid the influence of modulation depth fluctuation on the solution accuracy.