Before the development of the old mining areas, it is necessary to use geophysical methods to detect the small coal goafs left in the mining area. Usually, private small coal mines are not large in scale and shallow in depth. If it is located in mountainous areas, some of geophysical methods will be difficult to lay out long survey lines due to the influence of topographic relief, resulting in certain limitations. In order to realize the accurate detection of shallow private mining tunnels under mountainous areas, firstly, we discussed detection effects of three common devices of ERT on low-resistance abnormal bodies by numerical simulation. Then, the response characteristics of small-loop TEM to good conductors at different distances are studied by physical simulation. Finally, in field experiments, the above two methods were combined to detect shallow private mining tunnels in Zhijin County, Guizhou Province. The experimental results show that small-loop TEM can overcome the problem that ERT is not easy to arrange long lines in mountainous area, and ERT can make up for the shortcomings of TEM shallow detection blind area and insufficient resolution. In the process of detecting the private mining tunnels, TEM can be used for preliminary detection to provide some geophysical information. Based on this, more short ERT lines with higher resolution is laid out to accurately detect the tunnels, and TEM inversion data can be corrected with the ERT resistivity data and achieve more accurate results. The combination of the two methods reduces the limitations of only single geophysical method in the interpretation of inversion results, and provides a reference for the accurate detection of geophysical methods in the shallow private mining caves of small coal mine.