Based on the LabVIEW platform,we have studied the distribution situation of the signal energy by the joint time frequency analysis method.This method has used the short-time Fourier transformation basic principle,and analyzes some non-steady signals such as the linear frequency modulation signal,and the method can describe how the signal frequency changes along with the time well,then can distinguish the signal very easily.This method has certain superiority compared to analyzing the signal by using the time domain or the frequency range alone