Abstract: Due to the complicacy in the selection of steel portal frame beam and column cross-sections and the discrete nature of their design variables,it is difficult to obtain satisfying results with traditional optimization methods.In this paper,the authors used MATLAB to make the structural optimization program of portal frame based on the Technical Specification for Light_Weighted Steel Portal Frames of China.The method of optimization is a discrete variable and genetic algorithms method.The examples illustrate that this method is very efficient,simple and easy to program.What's more,the GUI of optimization program is explored so that it is much easier to use optimization program.