In order to study the biomechanical response and injury mechanisms of pedestrian`s lower limb during impact, a three-dimensional FE model of lower limb for adult pedestrians with high precision was developed on the basis of human anatomical structure. The lower limb model included complete anatomical structure of femur, tibia, fibula, patella as well as soft tissues such as skin, fresh, ligaments, capsule meniscus and cartilage. Considering the nonuniformity of the section of cortical bone, a long bone model was developed based on CT data with the thickness and the shape of the cortical bone section varying continuously. In comparison with other modeling methods, cortical bone was modeled with two-layer solid elements to obtain higher precision and efficiency. The injury criterions of pedestrians′ lower limb such as the ultimate bending moment of femur and tibia were obtained by modeling related biomechanical experiments. In addition, the influence of the thickness of cortical bone and the impact direction to injury mechanism and injury parameters of lower limb were analyzed. The injury parameters can provide important reference for the design of cars.