Based on the comprehensive analysis of geology and hydrogeology conditions about 9# coal in Dongjing of Gequan coal mine, the abnormal regions were detected and grouted by use of integrated exploration technique. The hydraulic connection among aquifer in Ordovician limestone and Daqing limestone were cut off by grouting reconstruction and fracture sealing for coal floor. The lower coal seam suffered from Ordovician limestone water invasion was mined safely. The technology for prevention of mine water was summarized,which has guiding significance for the lower coal seam mined under similar conditions in this area or nationwide.