Due to close to the outcrop boundary, there is a large range of small coal mines with a long mining age in the southern part of Sunzhuang mine field. At present, small coal mines have been closed. Due to the unknown range of goaf formed by small coal mines and the unclear mining depth, the goaf of water accumulation area formed by small coal mines has a great impact on the safe mining of coal seams in the lower part of the mine. In the distribution area of small coal mines, transient electromagnet exploring depth was used to detect the distribution characteristics of low-resistance abnormal bodies in the target area, and infer and delineate the water abundance and water-accumulated abnormal areas. Based on the transient electromagnet exploring depth data, the resistivity-inversion section map was obtained, and combined with the known hydrogeological data in the area, the spatial occurrence state and range of the suspected goaf of water accumulation area in the main coal seam of the small coal mine were explained and inferred. After the later drilling verification, the location of some goaf of water accumulation area was basically consistent with the location of the abnormal area inferred by transient electromagnet exploring depth. This exploration provided technical support for the next step of transient electromagnet exploring depth method to explore the goaf of water accumulation area of small coal mines in the mining area and surrounding adjacent mines.