Abstract: Acoustic signals due to leaking in a liquid-filled pipe were measured with water as experimental medium. Wavelet transform was applied to these signals acquired at different flows and different diameters of leaking holes to analyze the spectrum characteristics. The results show that the leaking signal of liquidfilled pipe can be analyzed by wavelet. Most of the leaking acoustic emission is concentrated at the a6 level and its main frequency components are within 3.05~3.81kHz.