In this paper, a two-stage optimization approach for structural dynamic design was proposed on the basis of Component Mode Synthesis (CMS in short) technique. To improve the convergence of the optimization, the optimization was decomposed to two stages, i.e. the global and the local stages. The dynamic performance of the global assembled structures was optimized at the global stage by minimizing the total mass, taking the position of nodes as design variables. At the local stage, the performance of the local components was optimized by keeping the component mass less than the initial value, and getting the performance of the global structure improved. The CMS technique was integrated in the optimization to reduce the modeling cost and to determine the objective function of the local stage optimization. The dynamic optimization of the metal structure of an escalator was taken as an example to illustrate the feasibility and effectiveness of the proposed approach.