Abstract: It is known that the phenomenon of high pressure, water leakage, fully mechanized supports crushing frequently occurs in the roof of working face with large mining height, which under thin bedrock and thick weathered or oxidation zone. In this study, a new type of L-shaped directional branch hole structure is adopted to pre-grouting the thick weathering and oxidation zone, so that some reasonable grouting parameters and grouting technical measures are designed for prevent the supports crushing accident during coal mining. Engineering practice show that, ground pregrouting with multi-permeability source is used to reinforce the seam in weathering and oxidation zone, which can bear high grouting pressure, improves the mechanical behavior of overlying surrounding rock structure, filling the water channel of upper aquifer and block the cranny water of coal seam roof. On that basis, high-strength hydraulic support is used suitable, then safety mining is accomplished. research provide a new technical approach for mining under thin bedrock coal seam of the similar geological conditions.