Abstract: The stiffness optimization subjected to the constraints of shear, bending, or torsion force, and the buckling optimization subjected to the constraints of axial and shear forces of beam structures with five kinds of commonly used cross sections are studied in the paper. The design variables include the sizes and the shape of beam cross-section, and the optimizations have been performed with JIFEX, a general-purpose software for the finite element analysis and design optimization. Some useful conclusions for engineering design are drawn by analyses of the computational results of design optimization. Additionally, a wave-shaped beam of aeroplane structure is optimized and the influence of wave number on the structural buckling stability and stiffness is discussed.