Coal pillar exerts great importance of safe and efficient mining in working face, the size is an important factor that affecting the cost of roadway maintenance and raw coal mining. Based on the stability factor of coal pillar in some mine of Shanxi province, 1306 working face of the mine was taken as the experiment site, the reasonable size of coal pillar was analyzed and conducted with numerical simulation, the reasonable net width of coal pillar of the working face was not less than 40 m, which had guidance significance for safe and efficient mining in large mining height working face.