Abstract: A optical distributed vibration sensing(DVS) scheme based on the space difference of Rayleigh backscattering was presented for perimeter security. In this scheme Rayleigh backscattered light with phase changes induced by vibration signal along the sensing fiber was split and fed into an imbalanced Michelson interferometer. The space difference of Rayleigh backscattering was realized. The DVS system realized the phase demodulation of the Rayleigh backscattered light to improve the sensitivity of the system. The distributed vibration sensing system based on space difference of Rayleigh backscattering can restore the walking route, the velocity of the intruder and the distance of the simulative digger, and obtain the demodulated signal SNR of 15 dB and detection distance of 35 m.