Abstract: A diagnosis and signal analysis method with FFT signal processer is provided for on surge-detonation of a twin-spoot turbojet engine.The experimental investigation surge-detonation under a turbulent dynamic inlet distortion conditions has been completed by this method and the measuement system and test equipement are described.From the FFT analysis are drawn the conclusions:Most of surges in the turbojet compressor under turbulent dynamic inlet distortion conditions are “drift-mode” surges and appear randomly;The turbojet is far more sensitive to dynamic inlet distortion than to steady inlet distortion.It is shown that the signal analysis method with the FFT signal processor is of great practical value in the failure diagnosis,and it is a more accurate,reliable and convenient than others.under turbulent dynamic inlet distort