Aiming at the limitations of traditional theoretical calculation methods and physical model test techniques in analyzing large deformation and damage of the structure，a finite element simulation model was established based on slippage and damage of a dam in the flood season，combined with field survey and design data，and the contact surface of the damage site was reduced set up the shear resistance parameters and explore the real failure process of the structure.The research results show that when the shear resistance parameters on the contact surface are at the reference value，the structure as a whole is in the stage of elastic deformation；when the shear resistance parameters on the contact surface are reduced by 0.2 times，the structure failure form is basically consistent with the site survey.The research results can provide a reference for the next step of the project.