Based on time division multiplexing technology, a distributed weak fiber Bragg grating (FBG) array vibration detection system is proposed. By using a path-match interferometry method, the interference signals between two adjacent weak FBGs are detected, and relevant information of vibration such as phase, frequency and location is obtained, thus we can achieve high sensitivity distributed measurement. The 3×3 phase demodulation technique is employed to effectively eliminate signal fading in the interferometer. The feasibility of the system is verified by a weak FBG array with 660 gratings and 2.5 m distance between adjacent FBGs. Experimental results show that the interference fringe visibility is related to the wavelength difference between adjacent weak FBGs. Meanwhile, the proposed system can accurately distinguish weak signal with different frequencies (ranging from 20 Hz to 1000 Hz) and has better frequency response. The sensor system has higher sensitivity in contrast to standard seismic geophone.