Abstract: In order to determine the optimal length of 3505 working face of Liangbaosi Mine and the optimal width of the fault protection coal pillar, the FLAC^3D numerical simulation software was used to establish the calculation model. The effects of coal pillar width and working face length on the vertical stress distribution over abutment coal seam under different conditions were studied. The results show that when the width of the fault protection pillar is 45 m, the vertical stress peak of pillars is the smallest. With increase of the slope length of face, the vertical stress on pillars slowly increases in the interval from 60 m to 80 m, the vertical stress on the coal pillar rapidly increases in the interval after the inclined length is 80 m. According to the research and analysis of the simulation results and from the perspective of safety and economy, it is concluded that the ultimate width of fault protection coal pillar is 45 m and the inclined face length is 80 m.