Fiber Bragg grating (FBG) array has been extensively applied in variou s fields as a mainstream optical sensing technology. In an improved phase sensitive optical time domain reflectio n (Φ-OTDR) technology sensing system based on weak fiber Bragg grating (FBG) array,the Rayleigh scattering si gnals are replaced by the reflection signals of the weak FBG array,and the phase change is solved by a matching inte rferometer. In this paper,the effect of weak FBG array on the improvement of signal-to-noise (SNR) and the decrease of noise in a Φ-OTDR vibration s ensing system is studied,and the crosstalk caused by multiple reflections in the impro ved system is analyzed. The results show that compared with traditional Φ-OTDR vibration sensin g system,the system with －35dB reflectivity FBG array has a lower phase noise level and its SNR is improved by 33dB. Due to the influence o f crosstalk,compared with the first FBG,the noise at the end of the sensing fiber is increased by 18dB. However,th e performance of the system based on FBG array is still better than the Φ-OTDR system witho ut FBG array and keep a high SNR level.Thus,the introduction of weak FBG array has a positive influence on improving SNR and reducing noise.