Abstract: Double optimal design variables are reduced into asingle optimal design variable, and the optimization design model ofpre-stressed concrete filled square steel tubular column is establishedaccordingly. By using penalty function method, the iteration formulas ofoptimal design variables are derived, and the calculation procedure of thedouble iterative method is given in this paper. The numerical example showsthat it is simple in concept and convenient for solvingcross-section optimization design problems of pre-stressed square steel pipe concretecolumns, and it provides a better approach for nonlinear programming.