Based on the broad application prospect of distributed optical fiber sensing technology in the field of perimeter security, the modulation mechanism and demodulation principle of vibration signals on single-mode optical fiber are deduced and analyzed in detail, and a set of distributed acoustic sensor (DAS) system based on phase sensitive time domain reflectometer is constructed. A complete piezoelectric ceramic vibration signal detection experiment and voice and footstep signal detection experiment are designed. The intensity and phase demodulation of vibration signals are realized by moving difference summation and orthogonal demodulation algorithm. In the voice detection experiment, the sensitivity of optical fiber to sound waves is improved by using an iron semi-closed hollow cylinder. The subjective mean opinion value survey of the original voice and the repeated voice is made to verify the quality of the speech signal. The footstep signals collected by DAS system are analyzed and interpreted in the time domain and frequency domain, and the relevant features of the single-step signal is extracted and explained. The experiments prove that this system can realize complex voice and footstep signal detection in the transmission distance of 2 km, and the spatial resolution can reach 2.2 m, which can be well applied to voice and footstep monitoring in the perimeter security.