Abstract: To determine the reasonable width of the coal pillar in the 52107 material roadway of the Ehuobulake Coal Mine. Firstly, the limit equilibrium theory was used to obtain that the reasonable width of the coal pillar in the 52107 material roadway is 5.88 meters. Then, the FLAC^3D numerical simulation software was used to study different coal pillar widths. Five schemes with different coal pillar widths were designed for calculation and optimization. Four monitoring faces were arranged in the 52107 mining face to analyze the plastic distribution of the coal pillar and the distribution of the surrounding rock stress field under different coal pillar widths, as well as the width of the elastic core zone. The results show that when the monitoring face is 0 meters away from the 52107 mining face, with the coal pillar width ≥ 6 meters, an elastic core zone appears in the central area of the coal pillar closer to the 52107 working face. The elastic core zone increases with the increase of the coal pillar width, indicating that the coal pillar's resistance to instability and failure is constantly increasing. When the coal pillar width is 6 meters,the width of the elastic core zone reaches 2 meters, and the elastic core zone rate reaches 33%. Further research on the vertical stress distribution within the coal pillar shows that as the coal pillar width increases, the vertical stress distribution curve becomes flatter, indicating that the bearing area of the coal pillar is constantly increasing. The peak vertical stress gradually decreases. When the coal pillar width is 5-8 meters, the peak abutment pressure reduction rate is over 49.6%, and the stress concentration coefficient reduction rate is also over 49.6%. Based on the results of theoretical analysis and numerical simulation, the reasonable width of the coal pillar in the 52107 material roadway is finally determined to be 6 meters.