In this paper,a new multi-area optical perimeter security system ba sed on Michelson interferometer is proposed,combining with the advantage of field programmable g ate array (FPGA) and utilizing Faraday rotation mirror to overcome polarization induction signal fadi ng.The system can monitor a lot of areas independently at the same time.The structure of the syst em is simple with low cost.It also has high scalability.In order to identify the invasion signal ef ficiently and quickly,we extract three characteristics of signal based on the invasion and environmental noise vi bration features on time-domain.They are the threshold-crossing rate of each frame of signal,the number of alarm frames of each group of signals and the coefficient of variation of the ratio between the maximum and minimum values of signal of each group,respectively.Then we propose the method of quick decision of invasion on this basis.It can realize the purpose of identifying the invasion signals effectivel y,improving the accuracy and real-time performance,with reducing the false alarm rate as a result of enviro nmental noises,such as external slight disturbance,wind and rain.The experiment results show that the system′s correction alarm rate reaches 90% and the failure rate is under 2%.