Abstract: It is an important innovation to control the water damage of the coal seam floor by using the mine prevention and control technology combined with the ground L-shaped directional drilling technology and the ground grouting technology, which is based on the drilling and measuring simultaneous orientation techniques. And the system research of directional drilling technology, drilling equipment, drilling structure design and hole making process, formed a complete set of technology. This technology has achieved good construction effect in the grouting reinforcement project of L8 limestone aquifer in the 1801 working face of Zhaogu Coal Mine, which not only enrich and perfect the water damage prevention technology of coal seam floor, but also realize the large area coal seam floor advanced grouting reform, the safe and efficient mining of large mining deep coal mine high pressure coal seam is of great significance.