Abstract: The optimal topology design of satellite trusses with appended structures was performed.The main goal was to reduce the volume(or the weight) of the structure while satisfying the compliance and the natural frequency constraints.Semidefinite programming was used to avoid underlying difficulty of sensitivity analysis of multiple eigenvalues.The effect of stiffness and mass of appended structure on optimum topology result was presented and several optimum designs were compared with each other.Structural mass was greatly reduced using this optimization method.The second member in the optimal topology design was grouped for parameter optimization according to the engineering considerations and the final practical structure satisfying the satellite mechanical performance was obtained.