Abstract: In order to optimize the size of coal pillar and improve the recovery rate, theoretical calculation method and numerical simulation method were used to study the reasonable width of coal pillar in Tenghui Coal Mine. Combining with the actual geological conditions and mining conditions of 2-204 working face in this mine, the reasonable size of coal pillars for roadway protection is obtained by theoretical calculation method at first, then the different width coal pillars are simulated by FLAC^3D numerical simulation software, and the corresponding plastic zone map and horizontal displacement map are obtained. Finally, the comprehensive analysis and comparison of numerical simulation and theoretical calculation show that when the width of pillar is 27 m, the stability of roadway is relatively good, and the coal recovery rate can be effectively improved.