Abstract: Aiming at the serious deformation of roadway surrounding rock in fully mechanized caving face with large buried depth and thick coal seam, based on the actual production conditions of F6218 working face in Buliangou Coal Mine, the theoretical width of coal pillar should be 24.63 m by theoretical calculation, numerical simulation and field monitoring.FLAC^3D simulation is used to verify the effect of roof cutting and pressure relief, and the distribution law of stress and plastic zone of coal pillars with different widths is compared.The results show that roof cutting and pressure relief can cut off the stress propagation path of roof, and the effect of roadway protection is remarkable, and the width of coal pillar can be further optimized after roof cutting.When the width of coal pillar is 26 m, the internal stress concentration of coal pillar is relatively mild, the range of plastic zone is stable, and there is a certain range of elastic core, which meets the actual production needs of the site.The peeping of coal pillar drilling shows that there is a certain range of undamaged area inside the coal pillar after the 26 m coal pillar is cut, which is conducive to maintaining the stability of the roadway.