In order to realize the safe recovery of No.2 coal seam in Xinzhi Mine, it was decided to carry out slurry transformation on the floor of No.2 coal seam. By drilling and coring in the bottom slab and combining with the drilling data, the characteristics of fracture development in the roof of Ordovician tuff were obtained, and on this basis, the layer for grouting transformation was determined. By reinforcing the bottom plate with grouting, the hydraulic connection between the ash water and the mining area was reduced, and the amount of water during the workface recovery was small and no sudden water occurred, which achieved a better control effect and provided a reference for the management of ash water under similar conditions.