Abstract: In this paper,the overburden karst soil cave is taken as the research object. Through modeling and analysis,the mathematical model of the collapse caused by vacuum erosion caused by groundwater sudden drop is established. The stability coefficient expression of the excavated cave is obtained according to the Boyle's law,and the calculation formula of the negative pressure of the excavated cave is derived. The influence of the initial groundwater level,the depth of water level and the thickness of soil overburden on the stability coefficient of subsidence is analyzed by numerical examples,and the internal influence law is discussed. The results show that the collapse stability coefficient K is inversely proportional to the negative pressure ΔP of soil cave under the condition of underground water sag. The size and position of initial water level h' and the depth of water level drop ΔH are related to the formation of negative pressure ΔP of soil cavity(vacuum) and the change of stability coefficient K of soil cavity collapse. When the initial water level is h' and the depth of water level is ΔH,the thickness of overburden has an obvious influence on the stability coefficient of collapse. When the initial water level is medium high and the depth of water level is medium high,the stability coefficient of collapse is positively correlated with the thickness of overburden.