Abstract: To address the issue of suboptimal coal pillar width leading to resource wastage in the fully mechanized mining face of the thick coal seam at Xiaobaodang No.1 mine, based on the geomechanics and strength test of roadway surrounding rock, theoretical analysis and numerical simulation are adopted to optimize the size of coal pillar, and the reasonable width of coal pillar is determined by engineering analog and field measurement.The results show that the type of geo-stress field is σ_H>σ_v>σ_h type stress field, the maximum horizontal principal stress is NNE direction, the mining roadway is greatly affected by the maximum horizontal principal stress, and the coal rock mass in the roof and shallow side of the roadway is obviously damaged, and the cracks are relatively developed, while the deep rock layer is less affected by mining and has good integrity.Through theoretical analysis, engineering analogy and numerical simulation, the optimum coal pillar width is determined to be 20 m.The deformation of coal pillar side measured on site is within a reasonable range, which meets the requirements of use and effectively improves the resource recovery rate.