In order to establish typical deep deformation and failure modes for slopes in the Paleogene red-bed area of the Yellow River to Xining Diversion Project, and to identify deep failure-type slope deformation masses, based on investigation and analysis results of slope deformation and failure phenomena in the water supply area, the formation mechanism of each discovered deep-failure red-bed landslide mass was analyzed, and a reverse analysis was conducted to determine the geomechanical characteristics of natural slopes before the formation of red-bed landslides. Numerical simulations were performed to analyze the key factors causing deep deformation failure of natural slopes in the Paleogene red-bed area, and typical deep deformation and failure modes for slopes in the Paleogene red-bed area were established. Slope deformation masses with the geological structural characteristics of typical deep deformation and failure modes were identified in the Paleogene red-bed area, and a three-dimensional numerical simulation model was established to analyze the deformation and stability characteristics of these deforming slope under natural, seismic, and rainfall conditions, and identify deep failure-type slope deformation masses. The results show that the deep deformation and failure mode for slopes in the Paleogene red-bed area is related to the stratum rock segments. According to the established typical deep deformation and failure mode for slopes, a potential deformation mass is identified along the No.24 branch line of the water supply project in the Paleogene red-bed area, showing poor stability under rainstorm conditions.