Abstract: Based on the geological data of Yulin-Shenmu coal mine area, the authors summarized space combination of coal seams and aquifers in the study area. With three-dimensional numerical simulation method, based on the plastic condition, failure criterion and stress criterion, the authors simulated the height of water flowing fractures for different space combination of the first coal seam and aquifers. After comparison between borehole detecting results and numerical simulation results, it shows that the numerical simulation method is feasible. According to the numerical simulation results, the spatial distribution of water flowing fractures height in Yulin-Shenmu coal mine area was illustrated, and the general distribution rules of water flowing fractures height were summarized in this paper. The risk of coal mining water loss in Yulin-Shenmu coal mine area was summarized and the risk zoning of coal mining water loss was also made through comparison between water flowing fractures height and overburden thickness of the first coal seam . Controlling the mining thickness of water loss area is helpful to coal mining water preserve. This study is of great theoretical and practical value for late production safety in Yulin-Shenmm coal mine area.