In order to study the main mining coal seam of No. 5 and No. 9 coal seam influenced by water hazard in mining, the hydrogeologic condition of the coalfield was studied by geological survey, the main aquifer and its units-inflow were found. The result showed that hydrochemical type of aquifer is different, with little hydraulic connection or nothing, upper coal seam with weak water-bearing feature and mine inflow about 3 000 m3/d, which has no effect on mining in normal drainage. The upper coal seam with pressure mining caused by lower karst aquifer, water bursting coefficient less than 0.06 MPa/m, with possible water burst in weak floor.