Abstract: Based on complex geological conditions in Longgu Coal Mine, through the existing geophysical and drilling data, the statistical analysis was carried out about the hydrogeological overview of east third mining area. The layout and depth of extension roadway water exploration drilling was determined in the driving process of extended roadway, during the roadway excavation, the water-abundance detection of floor was strengthened and the program of water prevention and control was made. Combined with the distribution of relative water-resisting layer, in view of rock mechanics and floor water-abundance distribution, the grouting reconstruction position and thickness of roadway floor were determined.