Abstract: In order to study the large-scale unstable high-fill slopes,the hydrodynamic erosion has brought major disaster hazards.Taking the terraced loess fill slopes in Yan’an,Shaanxi Province as the research object,the deformation-mechanical response characteristics of the terraced loess fill slopes caused by the progressive rising groundwater are analyzed,combined with numerical and theoretical analysis results,the deformation mechanism and failure mode of the terraced loess fill slopes induced by hydrodynamic erosion are mainly revealed.The research shows that:the upper shallow layer of the terraced loess fill slope is mainly shear and tensile failure,and the deep part is mainly shear failure,but the front edge of the fill slope is mainly shear failure.As the groundwater level continues to rise,the plastic zone of the upper part develops upward gradually,while the plastic zone of the upper shear and tensile failure develops downward.For the terraced loess fill slope under the action of hydrodynamic erosion,only a small groundwater level is required to cause the migration of particles smaller than 0.015mm,while the particle size is larger than 0.015mm,the groundwater level required for particle movement increases rapidly.With the increase of particle size,the required critical groundwater level of the particles at the same position shows an obvious increasing trend.While for particles with the same particle size,the greater the distance from the free surface,the higher the critical groundwater level.