A method of fiber Bragg grating time-division multiplexing intensity demodulation based on Sagnac fiber ring is presented. The time-multiplexing sensing system， consisted of the several FBG gratings with the same central-wavelength， can demodulate the signals by observing the intensity changes of the output spectrum of the FBG gratings. In the signal processing module， the wavelet analysis and Gaussian simulation algorithm are combined to demodulate the system signal together. The experimental results show that the signal-to-noise ratio of the system signal is increased by about 36% from 8.06 dB to 11.7 dB， which effectively improves the anti-interference ability of the system and the detection accuracy for the external parameters. The proposed method effectively increases the number of fiber Bragg grating sensors in the demodulation system with less cost and can be widely applied to various sensor systems or parameter detection systems.