Abstract: In view of the lightweight of a composite air suspension guiding arm, inspired by the structural characteristics of cross-section shape, variable sections and joints of bamboos, this paper designs a bionic guiding arm through the structural bionic method. Through parameter sensitivity analysis, key parameters affecting the performance of the bionic guiding arm are firstly investigated. With a great influence on the performance of the guiding arm, the rib plate and inner hole cross-section parameters are then selected as the design variables. Besides, the total mass and the minimum value of maximum deformation of the guiding arm are selected as the optimized targets for multi-objective optimization. Finally, the optimal parameter scheme of the Pareto solution set is determined by combining entropy-weight TOPSIS-gray correlation analysis with the multi-objective decision method. The results show that, under the premise that the mass of the prototype guiding arm reduces by 17.44%, the bionic guiding arm after multi-objective optimization shows a decrease in the maximum deformation by 9.24%, a decrease in the equivalent force by 17.33%, and an increase in the first-order prestressed constraint mode frequency by 22.92%. The study in this paper strongly proves the feasibility of the structural bionic design optimization method in the lightweight design of the guiding arm, which has certain reference significance for the structural lightweight design of guiding arms.