We propose and experimentally demonstrate a method for measuring liquid phase diffusion based on tilted fiber Bragg grating (TFBG). By monitoring the transmission spectra of the TFBG placed at different positions of the diffusion zone and calculating the normalized area enclosed by the upper and lower envelope curves of the cladding modes, the distribution curves of the glycerol concentration are obtained, according to the experimental calibration formulas between the glycerol concentration and the normalized area. This method can conveniently achieve remote and distributed measurement of the liquid phase diffusion in hostile environment because of its all-fiber structure.