Abstract: The engineering system of structural optimization for spacecraft(ESSOSⅡ) was applied in the optimization design of a complicated satellite structure, in which the minimum weight was taken as the objective, the layer thicknesses of composite laminate panels as the design variables, and the frequencies and stresses under two structural cases of being launched (furled) and working in orbit (deployed) as the constraints. Based on finite element models of these two structural cases, twol-evel multi-point approximation method was adopted in optimum solution and in each optimization iteration finite element analyses were performed for both structural case models. Compared with the primal design, structural weight decreases obviously after optimization, and all constraints under furled and deployed structural cases were satisfied, which provide a basis for the engineering department to improve the primal design and meanwhile also show the effectiveness of ESSOSⅡ.