Abstract: By means of the pressure signals of a certain research engine which has an eight axial stage compressor.A method of time-frequency analysis is presented in the paper.Information on the stall inception and development,which has some correlations with the onset-frequency and stall-frequency can be obtained during the engine operations.Therefore,the two main frequencies at the stall inception can be observed in the time-frequency plots.In order to identify the signal of the onset of stall accurately,this paper introduces the technique of the wavelet analysis,and provides an example of the 1st-6th compressor stage signals which are decomposed by Daubechies wavelets.The result indicates that different frequencies show different stall inception prior to the stage stall,and proves the singularity of the signal of stall.The stage of the first stall is ascertained by this method in the paper.