Abstract: For fully mechanized caving face with high gas and fault occurrence, coal pillar with reasonable reserved width can not only support overlying strata pressure, but also isolate gas in goaf and reduce gas diffusion. However, there is a lack of research on distribution characteristics of surrounding rock stress under the condition of reasonable reserved width of different coal pillars at present, and it is difficult to accurately determine the basis for calculating reserved width of coal pillars because factors affecting coal pillar width in different mines are different. For the above problems, taking M9 -10 coal seam on fully mechanized caving face of Tunbao Coal Mine as engineering background, the minimum width of coal pillar is obtained by theoretical calculation, and stress distribution characteristics around coal pillars with different width are studied by numerical simulation. The results show that: reasonable coal pillar width is 30 -40 m; horizontal stress in coal pillar tends to goaf side with the increase of coal pillar width, which verifies that the increase of coal pillar width can transfer influence of horizontal stress on roadway, so as to improve roadway stability; vertical stress of coal pillar has characteristics of double wave peaks,and the vertical stress peak and stress concentration coefficient at roadway side and goaf side decrease with the increase of coal pillar width; location of stress peak at roadway side is 2.5 m away from the roadway, then as the distance from the roadway increases, the vertical stress first decreases rapidly and then increases slowly, and then slowly decreases after the stress peak appears on the goaf side. In order to verify rationality of 40 m coal pillar width, field monitoring of drilling stress and gas concentration is carried out on the fully mechanized caving face. The result shows that the coal pillar width of 40 m can meet actual requirements of roadway support strength and gas diffusion.