Abstract: The goaf at the side of the roadway pillar (lateral roof) often encounters thick and hard roof, which will not collapse naturally in a short period of time, and is easy to cause mine earthquake and roof fall. Taking the 113105 working face of Bojiang Haizi Coal Mine as the research background, aiming at the strong ground pressure phenomenon caused by the lateral long cantilever, based on roof fracture mechanics, a mechanical model of lateral long cantilever of goaf is established to analyze the fracture length of rock mass between the roof before and after roof cutting. The results show that when the tensile strength, thickness and friction coefficient of rock mass are large, the front beam length after fracture is longer; when the unit weight and cutting angle of rock mass increase, the back beam length after fracture is longer. Through physical test, the long cantilever broke into two 5-8 m long blocks after roof cutting, and the roof collapsed periodically, realizing the purpose of active pressure relief on the lateral cantilever rock layer of the roadway. The field test shows that the surrounding rock stress is transferred after the blasting roof cutting, the ground pressure manifestation is reduced, and the roadway deformation can meet the normal mining demand of the working face, ensuring the high production and high efficiency of the mine.