[Objective] Soil strengthening and slope protection effects of two kinds of herbaceous plants were explored on red clay slope in order to provide scientific references for the ecological management of this type of slope, river channel, and dam. [Methods] With red clay slope as the research object, Cynodon dactylon and vetiver grass were selected as slope protection plants. The slope protection effect of the two herbaceous plants was determined through planting tests, root tensile tests, direct shear tests, and indoor simulated scouring tests. [Results] ① Within 150 days of planting, both herbaceous plants grew steadily and the tensile strength of the root system continued to increase. From 30 to 150 days of growth, the maximum tensile strength of Cynodon dactylon roots increased from 0.84 N to 8.59 N, and that of vetiver grass increased from 4.78 N to 89.89 N. ② At 120 days of growth, the cohesion of the Cynodon dactylon root-soil complex was 91.1% greater than the cohesion of rootless soil, and the angle of internal friction increased by 12.45%. The cohesion of the vetiver grass root-soil complex was 107.47% greater than that of rootless soil, and the angle of internal friction increased by 12.74%. ③ The runoff rate of the Cynodon dactylon slope at 150 days of growth was 45.02% to 54.15% less than observed on a bare slope, while the sediment yield rate was 58.3% to 93.85% less, and the 60 min cumulative sediment yield was 81.02% less. Similarly, the runoff rate of the vetiver grass slope was 35.46% to 46.48% less than observed on a bare slope, while the sediment yield was 46.8% to 89.44% less, and the 60 min have sediment yield was 74.61% less. [Conclusion] Both herbaceous plants had excellent soil consolidation and slope protection effects on red clay slopes, with vetiver grass having a more pronounced effect on the increase in soil shear strength, and Cynodon dactylon having a more significant effect on soil and water conservation.