A fast response pressure probe was applied to test the rotating stall and surge of an axial and centrifugal combined compressor.The pressure signals were analyzed by utilizing the method of the time-frequency analysis based on the Morlet and singular value decomposition.The experimental results indicate that

at the stable condition

there are many main frequency components in the frequency domain but the amplitude is small

while

at the stall condition

the energy of the frequency components becomes larger.In the process of unstall to stall

the larger amplitude of the pressure fluctuation does not produced by the stall cell in this compressor.The compressor enters smoothly into the full stall condition from the modal wave.2 stall cells are measured around annulus and the propagation speed of the stall cell is from 44.8% to 45.9% rotor speed.