Abstract: Aiming at the problem of reasonable width of coal pillars in thick seam pre-mining roof slicing fully mechanized mining face, taking 1308 working face of a mine as engineering background, the reasonable width range, stress distribution law and plastic zone distribution characteristics of coal pillars are studied by theoretical analysis, formula calculation and numerical simulation, so as to determine the reasonable width value. Research shows: to ensure that there is no overlapping phenomenon of excessive stress in the middle of the coal pillar, the width of the coal pillar should be greater than 21.9 m. When the width of the coal pillar is between 14 m and 22 m, the elastic zone gradually forms in the middle of the coal pillar. The stress overlap of the two sides of the goaf is stronger, the peak stress is higher, and the stability of the coal pillar is worse. When the width of the coal pillar is between 22 m and 32 m, there is enough elastic zone width in the middle of the coal pillar, and the stress in the goaf on both sides is weak and stable. Therefore, the reasonable width of coal pillar is 22 m.