In order to analyze the stability of coal pillar in No. 3 coal seam section of Changcun Mine, the method of numerical simulation was adopted. The stress distribution and plastic zone distribution after coal pillar formation were simulated by FLAC3D numerical simulation software. It could be obtained that through numerical simulation, the stress state and failure depth on both sides of the coal pillar were very different, the main reason for this phenomenon was that the shape of the goaf was different, the stress on both sides of the coal pillar formed a symmetrical distribution, and the vertical stress of the coal pillar was inversely proportional to the distance of the working face of the station, the plastic zone ranged on both sides of the coal pillar was not the same, but the junction of elastic zone and plastic zone was the peak position of vertical stress. The plastic failure ranging on the left side of the coal pillar was inversely proportional to the distance from the working face of the measuring station, and the plastic failure range on the right side of the coal pillar was proportional, but the change trend was slow.