15449S working face of Jiulong Mine is under the environment of large mining depth and high confined water. Before the mining project, regional advanced treatment work, pre-mining comprehensive geophysical exploration work, and pre-mining underground drilling verification work were carried out. However, during the mining process of mining face, lagging water phenomenon of varying degrees appeared, which affected the safety production of the mining face. The research on the technology of three-dimensional grouting in the same layer for the prevention of water damage on the floor of the coal seam was carried out. Aiming at the increasingly severe situation of water prevention and control, by analyzing the water outlet mechanism of the floor of the 15449S working face, the cause of water damage and a set of deep mine water prevention technology was adapted to the working environment of high mining stress and high pressure water to achieve safe production on the working face.