This article introduces a digital signal processing method of Perimeter Intrusion Detection based on Fiber Bragg Grating(FBG),which is the Time-Frequency analytical method.On the basis of the in-time signal analysis,It could finish the intrusion pattern recognition and analysis by transforming the in-time signal into the in-frequency signal and the results also are proved by using MATLAB simulation.This Time-Frequency analytical method resolves pattern recognition problem that exists in the pure time analysis.