The Xiyu conglomerate formation in Xinjiang Province is prone to significant slope toe erosion, which poses challenges for hydropower project construction in the area. To address this issue, the deformation and failure characteristics of slopes in Xiyu conglomerate subjected to toe erosion were investigated by exploring 16 parts, and the mechanical properties of the Xiyu conglomerate were studied. Using simulations with the discrete element method (DEM), the failure process during toe erosion was analyzed, and the influence of slope height on the failure mode of the slope was examined. A method for calculating the stability factor during toe erosion was proposed. The results revealed that the slopes in Xiyu conglomerate typically have a height of 10–30 m and a gradient angle of 85–90°. Xiyu conglomerate’s mechanical characteristics showed significant water weakening effects during toe erosion, which was the primary cause of slope failure. The toe erosion failure model changes from overall failure to partial failure, followed by overall failure, as the slope height increases. The toe erosion failure process can be divided into four stages: toe erosion, local collapse, vertical crack formation, and overall collapse. The safety factor of the slope varies during these stages, with a significant decrease observed as toe erosion depth and crack length increase. Interestingly, the safety factor of the slope increases with the increase in slope height.