In order to identify the characteristics of a turboshaft engine during surge, the bench test of a turboshaft engine was carried out by inlet distortion method, and the sound pressure signals on both sides of axial compressor and centrifugal compressor were measured and collected by sound pressure sensor. The test environment and background noise of sound pressure signal were corrected, the characteristics of compressor blade stall mass and low-frequency surge caused by intake reduction were detected by time-frequency analysis method, and the surge signal of a turboshaft engine was extracted and identified by wavelet low-frequency reconstruction of sound pressure signal. The results showed that with the increase of intake air, the amplitude of sound pressure signal at the rotor frequency of axial flow compressor and centrifugal compressor decreased, and stall mass was generated. Surge can be first detected on the right side of axial flow compressor, with the surge frequency about 60 Hz.