Abstract: By means of field geological survey, drilling, rock and soil sample testing, the geological conditions and formation mechanism of karst collapse in Jiangdong Village, Jinting Town, Suzhou City were studied in this paper. The carbonate rock in Jiangdong Village is characterized by pure quality, thick layers and high degree of karst development, with a relatively thin quaternary overburden of which the mechanical strength decreases greatly when it is exposed to water. These are internal geological conditions for the formation of karst collapse, and mining is the external inducing factor for the formation of collapse. The collapse model can be generalized as vacuum erosion-gravity collapse, which is mainly caused by vacuum negative pressure erosion-induced by gravity flow and rapid drop of water level in the cave pipe and the self-weight of overburden soil. According to the geological conditions and the induced factors of the collapsed area, a mechanical model of vacuum erosion-gravity induced collapse based on limit equilibrium theory was established. The calculation result of the model shows that the stability coefficient(K>1.0)of the collapsed body is bound to produce shear deformation and failure during the formation process of vacuum erosion. The model calculation result is in line with the actual situation of karst collapse.