Abstract: ［Objective］The temporal evolution of the soil stabilizing effect of vegetation on the Loess Plateau remains unclear, and the mechanisms by which the temporal dynamics of root growth influence the mechanical properties of the root soil complex have yet to be studied, which limits the long term evaluation of ecological slope protection［Methods］Vetiver grass (Chrysopogon zizanioides), tall fescue (Festuca elata), and Chinese silver grass (Miscanthus sinensis) were selected as study subjects. Using triaxial specimens to simulate in situ planting and controlled conditions in a climate chamber, the stress strain characteristics, shear strength parameters, and root morphology indices of the root soil complex were systematically measured at the 30d, 60d, and 120d growth stages.［Results］All three root systems produced a significant reinforcing effect, with the soil stabilization performance ranked as follows: vetiver grass > tall fescue > Chinese silver grass; at 60d, the shear strength of vetiver grass increased by 36.9% to 44.4% compared to bare soil. Shear strength exhibited a pattern of initial increase followed by a decrease, peaking at 60是d, with cohesion values of 24.25, 18.24, and 15.71 kPa, respectively. Although there was a decline at 120 d, the values remained significantly higher than those of the bare soil; SEM analysis revealed that during the growth peak, a dense micro interlocking structure formed at the root soil interface, which served as the basis for the increase in strength. In the later stages, root cortex aging and interface delamination led to a decline in soil stabilization efficacy. Vetiver grass established the optimal shear resistance system by leveraging its maximum root surface area and skeletal network［Conclusions］The study reveals the temporal evolution and mechanical characteristics of the soil stabilization effects of herbaceous root systems, confirming that 60d is the optimal duration for soil stabilization, and provides a reference for the selection and evaluation of the effectiveness of ecological slope protection plants on the Loess Plateau.