Two satellite structures were optimized using a structural optimization system that was secondary developed on the base of the commercial finite element software Patran/Nastran. The mass of structure was taken as the objective function and frequency and stress constraints were considered in the optimization. The system provided a Patran environment for users to establish the model of problem, while Nastran was executed as structural analysis code and the optimizer was based on two-level multi-point approximation method. The designed examples were typical complex structures of spacecraft constructed by honeycomb sandwich panels, shells as well as beams with various cross-sectional types. Man-machine interactive ways were also adopted and the structural masses were obviously decreased. The work supplies useful datum for the industrial departments to improve the current designs. The results of the developed system comply well with other’s for one of the examples, and the validity of the system is further verified.