Abstract: This study is to determine the width of section coal pillar for fully mechanized top coal caving face with hard roof and extra-thick coal seam. The W1123 working face in the Kuangou coal mine was selected as a case study. Based on theoretical analysis, numerical calculation and engineering practice, the reasonable width of coal pillar is determined. The research indicate that the stability of segment pillar is mainly affected by the main roof breaking and repeated mining. when the coal pillar width is 5~10m ,the stress of pillar inside is higher, the plastic zone is connected and its area is large. When the coal pillar width reaches 13~20m, the distribution of stress is relatively smooth, the peak value of stress decreases gradually, and the percentage of plastic zone decreases rapidly to 28%、16%and 6.3%. On the basis of considering the stability of roadway and improving the recovery rate of coal resources, the reasonable width of coal pillar is determined to be 15m, meanwhile the combined support systerm of “bolt+cable+anchor net+steel belt” be put forward. The research results can provide a useful reference for the determination of coal pillar with similar engineering conditions.