In order to improve the application effect of fiber grating, a high-speed and accurate fiber grating signal demodulation scheme is designed. According to the demodulation principle of LPFG fiber grating signal, two LPFG double-edge filters are designed to process the two reflected light, and the photodetector is used to detect the optical power result, so as to demodulate the central wavelength of the grating. The optical fiber interferometer is used to detect the demodulation frequency and perform positive and negative scanning. The demodulation result is compensated according to the correlation between the demodulation error caused by optical propagation delay and the scanning direction of demodulation frequency. The test results show that the scheme has good feasibility. The standard deviation of demodulation results of FBG signals is less than 1.85pm when the spectrum overlaps in different degrees. The demodulation error of grating wavelength is between -5~5pm. Effectively reduce the demodulation error, improve the demodulation accuracy of fiber grating, and obtain the information in the signal reliably.