The invention discloses a multi-channel fiber Bragg grating (FBG) demodulator, which adopts a scanning fiber laser as a light source. The scanning fiber laser is on the basis of a micro-mechanical structural filter with temperature control, and belongs to a narrow-linewidth and high-coherent light source which is calibrated accurately. The calibration is implemented by a thermostable FP etalon with a wavelength label. A gain matching fiber amplifier amplifies the power of the output of a laser and achieves the power flatness of scanning laser spectroscopy. A fiber Bragg grating reflected signal enters a data acquiring and processing system after passing through a photoelectric detector and an AD converter processing module. A data acquiring and processing and peak detection system is implemented by adopting an FPGA-based all-digital scheme, and simultaneously utilizes a synchronous signal of a direct numerical frequency synthesis module to obtain a control voltage of the micro-mechanical structural filter. By combining with other equipment, the scanning fiber laser, the etalon and the FPGA realize the multichannel, high-precision, high-stability, high-repeatability, and serial-parallel structure detection of a grating sensor network signal.