Abstract: There are many factors affecting bank collapse, and the causes are complex. Most of the existing studies focus on a single factor, and the relationship between the factors is unclear. Combined with laboratory flume test and numerical calculation, the process of bank collapse under the action of multiple factors is analyzed, and the mechanical mechanism of bank instability is revealed. The analysis results show that shear, tension and axial failure as well as soil shedding caused by the reduction of matrix suction are the main types of bank collapse caused by lateral flow scouring. The reduction of relative water depth (bank height/near shore water depth) causes the bank failure type to change from axial failure to shear failure. The joint action of seepage and lateral flow will greatly accelerate the bank collapse process.