Abstract: Large-scale suspension structure is formed after mining of 31319 fully mechanized working face of Cahasu Coal Mine.The cantilever beam is longer and difficult to collapse, which produces a superposition effect to cause the cantilever beam to break and severely threaten the safety of coal mines.The research on hydraulic fracturing technology was carried out on the coal pillar side of 31319 fully mechanized working face, and on-site industrial test and numerical simulation were conducted.The results show that hydraulic fracturing technology has a good effect on weakening the strength of the roof.After the hydraulic fracturing is taken, seams generated by the pre-split destroys the integrity of roof, and cuts off the stress transmission path between roofs.Under the impact of mining in the working face, the periodic and orderly collapse of roof is achieved.The numerical simulation results show that the pre-spliting roof cutting is cut off the connection between the roofs, the roof of the working surface can be collapsed in time, and the peak stress value of the coal pillar is significantly reduced from 28.7 MPa to 21.3 MPa, which proves that weakening the strength of the roof by hydraulic fracturing is effective.