Based on surface subsidence of transportation roadway and underground roadway collapse caused by water in Dongqu Mine, hydrogeological survey of water coal seam was analyzed, the reason of surface subsidence and roadway flooding was studied, water prevention by drilling grouting was put forward. The practice showed that the technology could block the outlet water points and avoid surface subsidence and water gushing in underground roadways, meet the requirements of the Provisions on Prevention and Control of Coal Mine Water, ensure the safe mining.