Located in the Three Gorges Reservoir area, the Jinyun Mountains of Chongqing City is the national natural reserve. Due to the topographic characteristics, soil erosion and shallow landslides are easy to occur on slope. Therefore, effective disaster prevention without destroying original ecological environment is the key control work in this region. Pinus massoniana Lamb as Coniferous species and Gordonia acuminate as broad-leaf species, with the same root architecture, were selected, and their relative effects on the increment of soil shear strength were compared. Effects of crucial factors, e.g., root area ratio, shear zone root diameter level, spectrum of root position and angle distribution, on the shear strength were further discussed. Results show that the soil reinforcement effect for coniferous species was greater than those for broad-leaf species. The greater averaged tensile strength of coniferous tree led to a larger increment of soil shear strength. The coniferous species, presenting better steadiness on slope, had a larger spectrum of root position distribution and a greater amount of roots at an angle of 60° with shear direction. Effect of the root area ratio to soil shear strength is not notable.