Fiber perimeter security system based on dual Mach-Zehnder interferom eter (DMZI) is a kind of sensor system that uses fiber as the sensing media.The endpoint detection in the fiber perimeter security system can confirm the start of the disturbance signal,which is the ba sis of disturbance position calculation and action mode judging.In order to improve the performance of the disturbance signal endpoint detection and the accuracy of position,this paper presents a novel end point detection method. First,through calculating the short-term energy and zero-crossing rate of the signal,the signal points which can meet some thresholds are found respectively.And then by weighing the t wo signal points,the endpoint of the disturbance signal can be obtained.Compared with the discrete wavelet me thod,this method analyzes short-term energy and zero-crossing rate synthetically,and is able t o accommodate more types of disturbance events,improving the precision of endpoint detection great ly and reducing the computation time significantly.Experimental results show that the method achieves that 93.47% of the position error is less than 10m with calculation time less than 0.3s,in the case of 10MHz sampling rate and 0.3s signals.