Based on the analysis of the hydrogeological characteristics of the area and the minefield and the observation of the downhole hydrogeological phenomena, it was considered that the coal seam No. 5-1 in the 4-2 coal mining at present was dominated by the overlying direct aquifer, the main channels were faults, poorly closed boreholes, roof caving, water-conducting fractures and floor rock fractures. The results showed that in No.4-2 coal mine, the direct water-filling water source of No.5-1 coal seam was clastic rock pore-type and fractured submarine bearing aquifer, and the potential water-filling source was goaf water. At the same time, forecasting the amount of water in the mine, and some suggestion of mine water damage prevention and control work was put forward.