Abstract: he caved roof can not effectively fill the goaf during the mining of thin direct roof, which causes the long cantilever structure to form on the thick and hard base roof and squeeze the roadway.Based on the conditions of thin direct roof and thick basic roof on 1103 working face of a mine, a fracture mechanics model of cantilever beam on the bottom slit basic roof was established.The calculation method of the resistance of the side cut roof when the basic roof is broken is deduced and reasonable cutting top parameters are determined by numerical simulation.The results show that:When the side length of cantilever roof and rock loading parameters, such as certain, lane escribed jacking resistance after the first increases with the increase of cutting the top height is reduced, to make thick overlying roof along the slip surface rupture and instability of kerf width, reasonable cutting parameters should be cut top height 4 m, kerf Angle of 10 °, the lane beside provide the cutting resistance of at least 3350 KN.The research results have been successfully carried out in the field engineering, which can provide reference for similar engineering projects.