The phenomenon of sinkholes in soil stratum induced by subterranean cavity is the common geological hazards. However, there is limited research on the formation mechanisms of sinkholes due to its complicated reasons. In this paper, the formation models of sinkholes in soft and coarse-grained soil strata are firstly obtained by analyzing the formation causes and case studies. For the cylinder-shaped sinkhole in soft soil stratum, the equations of safety factor are derived using the plastic limit equilibrium theory, which are further used to characterize some relevant factors that influence the formation of sinkholes. For the funneled sinkhole in coarse-grained soil stratum, the equation of safety factor is also determined on the basis of the granular media flow theory. By analyzing the formation patterns of sinkholes, we propose a method to predict and assess the sinkhole occurrence based on the thickness of soil stratum and the maximum subsidence. Finally, the deformation characteristics of the soft and coursed-grained soil strata induced by sinkholes are analyzed by using numerical simulation, and two formation models of the sinkholes are further verified. This study is essential to understanding the formation mechanisms and prevention of sinkholes in soil stratum.