Abstract: In view of the disaster caused by the instability of room-and-pillar goaf, taking the coal pillar left over from a pillar goaf in Yulin as the research background, the roof instability mechanism of room-and-pillar goaf is studied by means of theoretical analysis, physical similarity simulation, numerical analysis and so on. The research results show that the safety factor of the stability of the remaining coal pillar in the mine goaf is 1.54, considering the creep of the coal pillar under the long-term roof load, the large area instability will occur in the end. The influencing factors of the failure and instability of the coal pillar in the room-pillar goaf include five factors, such as physical and mechanical properties of coal, weathering, mining mode, water erosion, creep and so on. The failure law of the catastrophic evolution of roof in room-and-pillar goaf is from point to surface, and the roof from failure to instability is divided into four stages: preliminary failure stage, failure expansion stage, failure aggravation stage and complete instability stage. When the goaf is completely unstable, the peak stress of coal pillar is 15.08 MPa, the stress concentration factor is 3.92, and the roof subsidence displacement is 392.44 mm.