Based on geological conditions of cuijiazhai coal mine engineering, two methods of theoretical calculation and numerical simulation were adopted to study reasonable coal pillar width in No. 1 coal seam section. The width of section coal column was no less than 15.1 m through theoretical calculation. At the same time, the internal stress distribution of coal pillars in 5, 10, 15, 18, 20, 25 and 30 m was simulated by FLAC3D numerical simulation software, and distribution of vertical stress coal pillar and distribution of plastic area on either side of the coal column were obtained to verify rationality and objectivity of theoretical calculation. Finally, width of section coal column was determined to be 18 m after overall consideration of stability of pillar and recovery of resources. This method provided basis for retention of coal pillar in subsequent mining section and had certain reference value for coal mine under similar engineering geological condition.