Grassland vegetation was an effective measure to control slope erosion. However, information regarding how the erosion processes and control efficiency differ as functions of grass species combinations and components was lacking. In this study, a series of artificial rainfall events (60, 90, and 120mm h-1) were conducted on experimental plots (2 m×0.5 m) with a slope of 15° and treated with three different grass species combinations (Festuca elata (F. elata), Medicago sativa (M. sativa), and Festuca elata + Medicago sativa (F. elata + M. sativa)), with measurements of the runoff generation, sediment yield, and runoff velocity. A bare slope plot (BS) served as a control. Three erosion control scenarios were evaluated: intact grass, stems + roots, and root only.These results showed that the mixed grassland (F. elata + M. sativa ) demonstrated superior runoff and sediment reduction across all rainfall intensities, outperforming both monocultures, with F. elata showing greater efficacy than M. sativa under equivalent treatments. The above-ground components (stems/leaves) primarily reduced runoff volume, while roots dominated sediment yield reduction. Grassland vegetation regulated erosion dynamics mainly by its above-ground parts reducing flow velocity and increasing slope resistance. The mixed grassland (F. elata + M. sativa ) showed the greatest benefits in reducing flow velocity and increasing slope resistance among the three grass species combinations across treatments, with F. elata outperforming M. sativa under equivalent conditions. In addition, grassland vegetation enhanced soil erosion resistance mainly through its root growth activities improving soil properties in the topsoil layer. There was a significant difference in soil erosion resistance enhancement efficiency among grasses with different root systems. The ability of F. elata with fibrous root systems to strengthen soil erosion resistance was better than that of M. sativa with taproot systems. However, the mixed grassland (F. elata + M. sativa) performed the best in enhancing soil erosion resistance due to the obvious improvement of topsoil properties by its dense and fine roots. This study revealed that grassland vegetation could control slope erosion processes through the joint action of above-ground parts and roots to regulate erosion dynamics and soil erosion resistance, simultaneously. The more complete the vertical structure of grassland vegetation, the more significant the slope erosion reduction efficiency. The mixed grassland had the optimal effects on controlling soil erosion of loess slopes. These results could deepen the study on the regulation of slope erosion processes in grasslands and provide an important technological support for grassland restoration and management in the loess region of northern Shaanxi province.