Abstract: There are sophisticated theories in the study of fissures of river bank slopes,but the formation mechanism of deep-seated fracture located outside of the regular unloading zone has not been well interpreted.In the bank slope of a dam site of the abutment slope of Jinping first stage hydropower station,there are many deep-seated fractures which will directly affect the the engineering layout and endanger safety of projects.Based on the detailed field work, the formation mechanism of the deep-seated fracture is studied by physical simulation experiments,and credible conclusions are obtained in this paper.The results provide powerful evidence for primary field judgment.