Abstract: In order to improve the safety of coal seam mining under thick sandstone aquifer in Xunyao mining area, based on the production geological conditions of Chang'an Coal Mine, the height evolution law of the water-conducting fracture zone in the overlying strata of 4^-2 coal seam was analyzed by theoretical analysis, numerical simulation and field measurement, and the influential law of mining thickness and aquicluge thickness of fully mechanized caving face on water-conducting fracture zone was determined.Firstly, the height range of water-conducting fracture zone in 4112 working face is 39.02～134.89 m by theoretical calculation, and the height range of water-conducting fracture zone in 4112 working face is 49.1～123.2 m by numerical simulation.The above analysis shows that the water-conducting fracture zone leads to the aquifer of Yijun Formation and partially enters the aquifer of Luohe Formation.Secondly, due to the influence of mining thickness and mudstone aquicluge thickness, the height of water-conducting fracture zone in 4112 working face shows a development trend of ‘high-low-higher',and the water inflow shows a development trend of ‘higher-low-high'.The development height influencing weight of water-conducting fracture zone: mudstone aquicluge thickness > coal seam mining thickness.