Abstract: Leak solid acoustic waves are acoustic waves that are initiated by pipe leaks and propagate along pipe walls, and their wave velocities are critical to locating a pipe leak. For the mode T(0, 1), mode L(0, 1) and mode F(1, 1) in the low frequency band suitable for leak location, a method is proposed for calculating the acoustic wave velocity based on the simplified low-frequency dispersion equations. The method applies simplified low-frequency fluid loads and soil loads to pipes, thus establishing the fluid-pipe-soil coupling equations. The wave velocities of the different modes can be obtained by solving the coupled equations. The dispersion curves of three pipe materials, namely steel, HDPE and, ductile iron, are calculated for different fluid and soil conditions. The results show that: fluid properties have a small effect on wave velocities, while soil properties can have a significant and complex effect on wave velocities. The dispersion curve of a buried water-filled DN200 ductile iron pipe is obtained through a calibration experiment. The calibration result is in a good agreement with the result of the calculation method proposed, which supports the engineering application value of the method proposed.