Influenced by the physiological and genetic characteristics of plants, the mechanical properties of roots differ significantly, with the result that species vary in their ability to resist soil erosion. The selection of species to reinforce soil and prevent erosion is the key to improving not only soil and water conservation, but also vegetation and ecological restoration. Research to identify suitable plant species is still in its early stages, and studies addressing many issues are urgently needed. Caragana microphylla Lam, Salix psammophila C.wang & Ch.Y.Yang, Sabina vulgaris Ant, Artemisia sphaerocephala Krasch, and Hippophae rhamnides Linn are common plants used in soil and water conservation projects in the arid and semi-arid regions of Inner Mongolia. Rainfall is concentrated in summer with short-duration and high-intensity. The mechanical properties of roots differ significantly with growth period and soil moisture conditions. In order to study the mechanical factors influencing soil-reinforcement by roots and identify suitable anti-erosion plant species for this area, root tensile strength, root-soil surface friction, and root-soil composite shear strength of five plant species were studied. During the spring drought period and summer wet period, ten indicators of efficacy in erosion prevention (root-soil composite cohesion, root-soil composite equivalent friction angle, root-soil interface sheer strength, cumulative surface area, interface friction coefficient, representative root elasticity modulus, representative root constitutive properties, taproot tensile strength, lateral branch root tensile strength, length of cumulative root length) of the five species at the age of 3-4 (mainly 4) years were measured. The data were then analyzed using principal component analysis (PCA) with SAS9.0 software. The PCA results indicate that tensile mechanical strength had the greatest influence on soil reinforcement, followed by root-soil surface friction, and then root-soil composite shear strength. Based on these mechanical factors, the performance of the five species was evaluated. In order to maintain the integrity of the data and reduce uncertainty caused by subjective expert assessments, the variance contribution to the PCA of each of the three mechanical characteristics was used as to weight an analytic hierarchy process (AHP). The results showed the soil-reinforcement indices in the drought period were ranked Caragana microphylla Lam (0.834) > Salix psammophila C.wang et Ch.Y.Yang (0.303) > Sabina vulgaris Ant (-0.066) > Artemisia sphaerocephala Krasch (-0.206) > Hippophae rhamnides Linn (-0.864), while in the wet period they were ranked Caragana microphylla Lam (0.876) > Sabina vulgaris Ant (0.218) > Salix psammophila C.wang et Ch.Y.Yang (0.065) > Artemisia sphaerocephala Krasch (-0.404) > Hippophae rhamnides Linn (-0.755). The results suggest that species with better root tensile strength should be chosen reinforce soil and prevent erosion. Of the five species, Caragana microphylla Lam is the preferred soil-reinforcement and anti-erosion plant in arid and semi-arid regions due to its high root tensile strength.