Numerical simulation method of finite element is used to study the Rayleigh wave response of underground leakage channel under different Rayleigh wave speeds. By calculating a series of finite element models with different depths of seepage channels and different offset distances and channel spacing, the influence of changes in channel spacing and offset distance on the characteristic signals of the Rayleigh wave response is obtained in the actual detection process. It is summarized that the optimal choice of channel spacing in the detection process is 1m, and the offset distance is 7m when the leakage location is 10m or less, and the relationship equation between the leakage channel location and the optimal offset distance is fitted out when the leakage channel location is more than 10m, which provides the program improvement for the detection of underground leakage channels, and is verified in the engineering examples, which provides the theoretical basis and reference for the reasonable choice of the offset distance and the spacing of the channel in the engineering investigation.