Abstract: The height of water-conducting fractured zone is one of the most concerned factors in the “three under” mining of coal mines.It is of great significance to determine the development height of the water-conducting fractured zone for the safe mining and water disaster prevention and control of the mine.Haizetan Coal Mine is taken as the research object, and the hydrogeological conditions and water filling factors of the mine are analyzed.The theoretical analysis and numerical simulation method are used to simulate the caving form of overlying strata after the mining of 3^# coal seam in the mine.The results show that there are 11 aquifers and 4 aquicludes on the overlying of 3^# coal seam, of which 7 aquifers are weak water-rich, 4 are medium water-rich and 1 is strong water-rich.The 3DEC numerical simulation results show that the maximum development height of the water-conducting fracture zone is 41 m with the mining of the working face, which is close to the theoretical calculation of 41.44 m.It can be determined that the maximum development range of the water-conducting fracture zone of No.3 coal seam is about 41 m.Finally, the analysis of water filling factors shows that the main water filling source of the mine is the sandstone confined aquifer of the Middle Jurassic Yan'an Formation, the indirect water filling source is atmospheric precipitation and surface water, and the main water filling channel is the water-conducting fractured zone caused by mining.