The phenomenon of lateral erosion and collapse of bank is widely distributed in major rivers in the world, which is a kind of natural disaster with great harm. Seasonal frozen rivers are affected by the coupling of hydrodynamics and freeze-thaw, and the mechanism of bank collapse is complex. The research on the collapse process is of great significance to river bank protection and comprehensive river management. Taking the downstream part of the main stream of the Songhua River near the dam of Dadingzishan Aviation Power Project as an example, the BSTEM model was used to analyze the bank slope stability in different periods by considering the freezing and thawing effect, and the collapse process of the dual structure bank was simulated. The results showed that the stability of the river bank was higher in the dry and high water periods, and the stability was lower in the flood period and the receding water period, which was the stage of frequent bank collapse. Considering the freezing and thawing effect, the simulated river bank slope shape and collapse width were in good agreement with the measured values, and the amount of erosion and collapse was increased by 7%-41%. The research results can provide some reference for the study of river bank collapse in seasonally frozen areas.