Abstract: With the application of UDEC numerical tool, the authors studied the impact of the super-thick coal seam mining activities on aquifers in Dajing mining area of Eastern Junggar coalfield which is based on the characteristics of coal seam deposition.The results showed that there are four key strata layers and two aquifers in this mining area.And it also showed that the more of the subdivision of coal seam, the more of the subsidence and the height of fracture of overlying strata, and consequently the higher of the fracturing height of rocks happened for same coal mining thickness which caused much damage to aquifers.On condition of mining 24 m height and advancing 300 m, the key strata and aquifer No.2 were damaged and collapsed.And the main key strata plays a vital role in the movement of overlying rocks and damage to aquifers.