Abstract: Accurate detection of pressure line leakage is the key to ensuring the safe operation of boiler, and the audio frequency analysis is the main detection method. A method based on joint time-frequency analysis (JTFA) is proposed to study the time-frequency characteristics of boiler background sound and pressure line leakage sound for leakage fault determination. A dual channel audio signal acquisition circuit composed of pre-amplification, program-controlled filtering and gain compensation is designed. Fast Fourier transform (FFT) is used to obtain the generalized spectrum characteristics of the signal, the program-controlled filter is used to set a dynamic frequency window for the acquisition signal, and the short-time Fourier transform (STFT) is used to set a time window for the acquisition signal. The time-frequency characteristics of the signal are analyzed from multiple perspectives to determine whether there is leakage fault in the operation of the pressure pipeline. Compared with the traditional RC filtering and fast Fourier transform analysis method, the time-frequency analysis method with dynamic double windows can improve the sensitivity of leakage signal acquisition and the accuracy of leakage fault determination.