Abstract: There exists security risks of goaf group in many metal mines.Regular detection on mine goaf group was carried out based on CMS，forming a dynamic monitoring system and accurately obtaining goaf 3D boundary.The chain instability model of isolate pillars was constructed:the mechanics model of the roof-isolate pillar of goaf was put forward based on catastrophe theory，and the instability criterion of isolate pillar was proposed，to determine the reasonable safety thickness of isolate pillar and prevent from the chain instability of goaf group.The numerical simulation verified the rationality of the calculation.In the research，through accurately controlling the safety thickness of isolate pillars，the disaster induced by goaf group instability can be effectively avoided.The results provide reference for the design of mining scheme.

Key words: Goaf group, Dynamic monitor, Isolate pillar, Instability model, Disaster control