Abstract: The root system of vegetation has a significant effect on soil strength. The existing studies lack an analytical description of the stress state during root-soil complex failure. To quantify the contribution of vegetation roots to soil strength, a series of consolidated undrained triaxial tests are conducted to study the strength characteristics of the root-soil composite, and a root-soil composite strength prediction model is established based on the energy dissipation principle. Finally the experimental results and the prediction model are compared and analyzed. The results show that the root system can significantly improves the strength of root-soil composite, when the root concentration is 0.486%, the deviatoric stress of the root-soil composite increases by 1.70 times compared with the plain soil, and the shear strength increases by 72.1% compared with the plain soil, and the root system significantly improves the strength of the soil more when the confining pressure is lower. The internal friction angle of the root-soil complex varies less with the increasing root content, while the cohesion of the root-soil complex gradually increases with the increasing root content. The predicted values of the root-soil complex model are close to the experimental results, indicating that the model is of high accuracy and reliability. The research results can provide a reference for theoretical studies on the strength characteristics of root-soil composites and provide a reliable method for predicting the strength of root-soil composites.