Abstract: Sudden collapse in goaf is one of serious geological hazards in Yushenfu mining area. Adopting engineering ecological analysis and mathematical derivation, this paper analyzed disaster-forming conditions and disaster -inducing mechanism in goaf, built rock mechanic system of roof and residual coal pillar, and deduced mechanical instability criterion based on cusp catastrophe model. Taking Zaoshaogou coal mine as an example, the results show that the criterion is simple and practical, the reliable results could be acquired, providing a new approach for quantitative stability evaluation of goaf.