Abstract: According to the design experiences accumulated in engineeringover a long period, making resonable and valid simplifications, a corresponding mathematical model is obtained in this paper. Based on the sequential entropy iterative method of structural optimization improvedby the author, the optimal design of thislarge scale stnutur is possible to be performed. The rules about the influence of the major factors on the price of structure are profoundly investigated in the paper. The optimal range of major factors is given. The results give a reference to the design in engineering.