Abstract: ABSTRACT in order to further study the occurrence conditions and mechanism of the Covered Karst Ground Collapse(CKGC),on the basis of Luo Xiaojie's theory about CKGC,the geological phenomena, geological model, physical model and mathematical expression of the soil-cave type ground collapse are studied. The formation and development of soil-cave and ground collapse are two different phases of soil-cave type karst ground collapse. According to the macroscopic geological phenomena in the process of collapse, combined with the kinematic response characteristics of soil body and deformation of surrounding soil in process of deformation, the geological model of soil-cave type karst ground collapse is established. On the basis of this, the physical model of soil-cave collapse is further simplified. Combined with other major collapse mechanisms in the literature, the stress analysis on the roof of the soil-cave is carried out. Based on the limit equilibrium theory, a universal mathematical expression is proposed. After discussing the influencing factors of the critical thickness of soil-cave roof, it is pointed out that the critical thickness is positively correlated with the cave diameter, the load increment, and higher shear strength of the roof, negatively with lower shear strength.