Abstract: In order to study the influence of the coal pillar left over from close protection layer mining on the protection scope and protection effect of the protected coal seam, this paper takes a mine as the engineering background, and discusses the stress of the coal seam floor, the stability of the remaining coal pillar and its influence range through theoretical analysis and FLAC3D numerical simulation. The results show that by judging the stress state of the goaf pillars on both sides, it is calculated that 12 m is the range of the plastic zone, and the 5 m wide legacy coal pillars are damaged and cannot be stable for a long time. With the increase of the width of the remaining coal pillars, the stress concentration and influence depth gradually weakened. The plastic zone ranges from 32 m to 13 m of the overlying rock layer, and the protected coal seam 8 m below the mining face is significantly relieved, indicating that the residual coal pillar can effectively protect the stress state of the protected coal seam and has certain reference significance for maintaining the stability of the roadway.