Perimeter security is the first line of defense to protect the importa nt facilities and assets.The peripheral security technology and method of high performance can eliminate or reduce the threat from the outside world.In this p aper,a high sensitivity fiber optic vibration sensor is designed based on the p rinciple of wavelength selective reflection of narrowband fiber Bragg grating.A phase generated carrier demodulator is used to demodulate the vibration signal of the sensor and the high precision real-time demodulation of the vibration si g nal of the sensor is achieved.Many of the multiplexing techniques,including wa velength division multiplexing (WDM),time division multiplexing (TDM),and spat ial division multiplexing (SDM) can be directly applied,which makes it possible for networked/array FBG sensors to cover a large area.Vibration sensors are bu ried in the ground and have the ability of the remote and real-time monitoring w ithin the length of optical fiber deployment.The vibration sensor and the demod ulator are tested in the field and the experimental data are presented.Feld tes t results indicate that the response waveform of vibration sensor is obviously f or personnel within 70meters and for vehicle within 200meters by analyzing the energy spectrum and kurtosis of time-varying signals of sensors.So it can be us ed in a variety of fields such as border air port nuclear sites of the perimeter security technology.