No. 4 coal seam with large width fully mechanized mining face of Longquan Mine might develop hidden geological structures, such as faults and subsided columns. The water-rich and water-conducting of geological structures affected the safe recovery mining. In order to ensure the smooth recovery of the 4301 working face, the 4301 working face was detected and analyzed by the underground transient electromagnetic detection technology, and the water-rich condition of the main aquifer of the coal seam floor within a certain range inside and outside the 4301 working face was identified in advance. The development of water prevention measures provided a basis for geophysical exploration.