Abstract: In karst areas， ground collapse is a common geological hazard， which poses a great threat to the safety of infrastructure and people's lives and properties. Taking Beihuanxincun， Guigang city as an example， this paper studies the cause of the karst collapse and the law of its hazard by using the methods of geological analysis and particle flow discrete element numerical simulation. The results show that this collapse is caused by many factors， including the geological environment， groundwater level fluctuation， pipeline leakage and engineering construction activities. The silty soil formed by differential weathering of dolomite and limestone is easy to induce collapse of soil caves and karst. The collapse hazard can be divided into three stages： formation， development and the collapse. There are significant differences in the size， shape and influence of soil caves in different stages. During the formation and development of the soil cave， the surface settlement gradually decreases from the collapse center to the surrounding area， with existence of obvious settlement sensitive areas. The vertical free face at the edge of the collapse pit has tensile stress， which is easy to induce collapse again. The research results can provide a theoretical reference for prevention and early warning of karst ground collapse.