Abstract: This study is based on the 1005 working face of a coal mine in Shandong Province,this study combined theoretical analysis and numerical simulation to explore the influence of the width of coal pillar on the stability of surrounding rock. The research shows that the width of coal pillar is the key factor affecting the stability of surrounding rock, and reasonable width of coal pillar can effectively improve the bearing capacity and stability of roadway. Through theoretical analysis, the mechanical model of goaf excavation is established, and the reasonable width of coal pillar is calculated to be between 5.86 m and 6.89 m. FLAC ^3D simulation software is used to simulate and analyze the changes of roadway surrounding rock stress, coal pillar subsidence and horizontal displacement under different pillar widths in roadway driving and working face mining stages. It is found that the changes of mining and mining stages with pillar widths are similar. In terms of pillar bearing stress: With the increase of the width of the coal pillar, when the width of the coal pillar is greater than 4 m, the load stress of the coal pillar gradually decreases with the increase of the width of the coal pillar. Subsidence and horizontal displacement of coal pillar: with the increase of the width of coal pillar, subsidence and horizontal displacement show a gradually decreasing trend. It is determined that the reasonable width of coal pillar in goaf excavation of face in a coal mine in Shandong Province is 6 m.