[Objective] The slope protection effect of plants, the mechanical properties of the root system of vetiver and the factors influencing the strength characteristics of the root-soil complex were studied to provide a reference basis for plant slope protection engineering design.[Methods] First, an outdoor model box was used to simulate the filling of red clay on the slope for vetiver planting conditions, and the mechanical properties of vetiver and the factors influencing the strength characteristics of the root-soil complex were studied through indoor tests, such as a root pull test and undisturbed root-soil composite direct shear test. Through fitting analysis and Spearman correlation analysis of the test results, the relationship between root diameter and tensile properties of vetiver and the effects of different indices on the shear strength of the root-soil complex were obtained.[Results] The average stretching resistance of the vetiver root system was 19.05 N, and the average tensile strength was 20.12 MPa. The stretching resistance and tensile strength of the root system of vetiver had a significant power function relationship with root diameter. Root weight density(RWD)decreased with increasing soil depth. The results of Spearman correlation analysis showed that the RWD and cohesive force c of the root-soil complex had a positive and strong correlation (R=0.882).[Conclusion] As the diameter of the root system of vetiver increases, its tensile strength increases and its tensile strength decreases. The increase in RWD can significantly increase the cohesive force c of the vetiver-red-clay root-soil complex, but the effect of increasing the friction angle φ is not obvious.