The rule of full stress is the most direct and effective method of the optimal design for shape steel truss. The full stress optimal design study of shape steel truss is about the optimal design of the discrete variable, which is more difficult than that of the continuous variable. Through the section parameters in the table of the shape steel, the function of the section area and the inertial radius is created, the optimal design of the discrete variable is changed into the optimal design of the continuous variable and the computed efficiency of iteration is promoted. Lastly, the general program is studied. Through this program, the truss with different kind and different shape in various load case is designed automatically. The result shows that the computation efficiency and accuracy is increased greatly, the proposed method can be used in the optimal design of the large-scale truss and spatial truss widely.