Abstract: To obtain optimal topology shape and cables' pretension force for prestressed steel structure, a mathematical optimization model is established in such a form that the cables' pretension force and the structural topology are referred as the design variables, the Von Mises stress as constrain condition, and the minimum of structural weight as the objective function.In order to establish the model, the method of minimizing structural strain energy (maximizing structural stiffness) is applied to calculate the cables' pretension force, and then the method of evolutionary structure optimization is provided to minimize the structural weight through deleting elements with minimum Von Mises stress.The result of the examples coincides with corresponding structural performance, and this indicates the method in this paper is effective and efficient.