Based on the analysis of the geological structural elements and the hydrogeologic features of the karst collapse in the mining district under the condition of forced drainage, a model was established to simulate the geologic structure of the karst collapse area. Also, a corresponding geotechnical model was established which couples such factors as gravity, sucking erosion and seepage. Judgment criteria for karst collapse were obtained through quantitative analysis. Further, safety performance of the overburden above the corrosion cavity was evaluated using a safety factor F s . Therefore,engineering geologic evaluation of karst collapse can be quantitative , not limited to being qualitative, so as to raise the precision of prediction of the collapse area.