In order to understand soil reinforcement by root, to explore the role of soil-reinforcement by roots in soil conservation under different conditions, Pinus tabulaeformis roots anti-tensile strength and anchoring force, and the root-soil composite triaxial compression apparatus tests were carried out. Results showed that tensile resistance of Pinus tabulaeformis roots increased with increasing diameter according to a power function, but tensile strength had no obvious change rule with the increasing diameter. The root stress-strain parameters were different in different curves, and the quadratic polynomial model was very reasonable to describe its stress-strain response. All of them showed the single-peak curves with elastic-plastic material characteristics. Ultimate stress and ultimate elongation had no significant correlation with their diameters. There was an approximate linear relationship between root soil friction and root diameter. The larger diameter and deeper depth of root were, the bigger root-soil interface friction and the stronger anchoring role were. With the same diameter, it was found that root-soil complex shear strength increased with the increase of confining pressure. With the same confining pressure, shear strength of root-soil complex increased with the increasing diameter, and with the same diameter and confining pressure, the increasing influence with vertical root was better than that with horizontal root.