[Objective] Frequent loess landslides occur in the Ili Valley. This study investigates the root mechanical properties of dominant herbaceous plants in landslide areas and the mechanical strength of their root-soil complexes to provide a basis for vegetation-based slope protection and disaster prevention in the Ili region. [Methods] The Jialangput landslide in the Ili Valley was selected as the study area. Field vegetation surveys and laboratory experiments were conducted on four dominant herbaceous plants: Eragrostis lineata, Poa pratensis, and Medicago sativa. Shear tests were performed on Eragrostis lineata root-soil composites under varying vegetation cover (root content gradients) to reveal root mechanical characteristics and their influence on shear resistance of root-soil composites. [Results] Single-root tensile tests revealed the following tensile strength ranking: The tensile strength of individual roots ranked as follows: Festuca pratensis > Stipa capillata > Medicago sativa ≈ Vicia faba. Root diameter of all four plants showed a positive power-law correlation with tensile strength and a negative power-law correlation with tensile strength. Direct shear tests revealed that the shear strength of the root-soil composite for Stipa linariifolia exhibited an initial increase followed by a decrease with increasing vegetation cover, peaking at 50% cover (corresponding to root content of 6.71 mg/cm3), with cohesion increasing by up to 328.74%. [Conclusion] This study reveals the mechanical characteristics of dominant herbaceous plant roots and their mechanism for enhancing the mechanical properties of root-soil composites. It identifies the optimal vegetation coverage rate, providing theoretical basis and practical guidance for ecological slope protection and disaster prevention in the loess landslide-prone areas of the Ili Valley.