Abstract: The research on propagation characteristics of acoustic emission signals of pipeline leak can provide an important basis to the location determination of sensors and the parameters acquisition in pipeline projects. Medium type, pressure, flowrate and leak size have significant impacts on the amplitude of acoustic emission signals of leak, but no effect on propagation attenuation pattern of acoustic emission signal of leak. Gas leak generates a high amplitude acoustic emission signals, and the amplitude of acoustic emission signals from leak increases as pressure increases. With the increase of leak size, the amplitude of acoustic emission signals of leak rises first and declines later. By using FFT conversion and wavelet packet decomposition theory, the paper analyzes the variation characteristics of frequency when the signals pass through fange and valves during propagation. The results show that signals amplitude attenuation, about 11 to 15 dB, will happen when acoustic emission signals pass through flange, while little change occurs in signal frequency distribution. After acoustic emission signals of pipeline leak pass through the valve, not only the amplitude of the signals attenuates by 27 to 35 dB, but also the high-frequency components see a substantial attenuation (from 187.5 kHz to 312.5 kHz).