Abstract: High stiffness, high strength and low weight of the load-bearing structures is a long-term goal pursued by structural engineers. The existing structural optimization methods are usually based on the black-box model, and the optimization results are obtained by iterative search, which can not provide a reasonable mechanical explanation. Based on the theory of relative stiffness, this paper presents the calculation process of load path visualization. Then, the evaluation method of the load-bearing performance is established, which can provide theoretical guidance for the evaluation and optimization of the load-bearing structures. Furthermore, the design idea that the materials are arranged along the load path is proposed to realize the high stiffness design of the load-bearing structures. The method is applied to the evaluation and optimization of a control arm. And the results show that the load-bearing performance of the control arm is improved: the stiffness and strength are increased by 75.41% and 8.61%, respectively, while the weight is reduced by 8.91%.