Abstract: Wavelet transform,as a tool for signal analysis,is applied to analysis of compressor rotating stall signals.With the Morlet wavelet transform,the time-evolution of the unsteady signals during the stall inception and the local behavior in the casing treatment plenum are investigated.By comparison with structure characteristics of the coherent waves in the casing without treatment,it is shown that the casing treatment do has different influences on pressure impulse signals.A mechanism for restraining perturbations of stall inception via casing treatment is proposed.