Abstract: With the gradual increase of buried depth of coal seam and the increase of coal demand, the deformation and failure degree of roadway and coal pillar are also intensified. In order to solve the problem of roadway instability, it is particularly important to study the reasonable size of coal pillar. Therefore, this paper takes the 214203 working face of Hanjiawan Coal Mine as the research object. To address the problem of insufficient basis for the width of coal pillar in Hanjiawan Coal Mine, the theoretical analysis is carried out by establishing the stress model of coal pillar, and the width of section coal pillar under this condition is studied. The results show that the development of plastic zones on both sides is different due to the influence of mining disturbance and roadway excavation, and it is calculated by SMP criterion. The plastic zone of the section coal pillar on the side of the goaf and the side of the roadway is 1.31 m and 2.93 m, and the range of the elastic core area in the middle is 5.14 m. Through numerical simulation analysis, it is found that when the width of the section coal pillar is 15 m, the width of the plastic zone is 1.9～2.3 m. According to the monitoring of the range of the loose circle of the coal pillar on the spot, the maximum depth is 1.4 m. On the basis of reducing the width of the coal pillar, there is no large deviation in the range of the plastic zone of the coal pillar. Therefore, it provides reasonable theoretical support for the safety of the mine, and also provides reference for the surrounding mines.