Abstract: According to the static and stable characteristics of cable-supported lattice shells, from the view of engineering application, based on geometrical nonlinearity, study has been made on section optimization under determined cable forces by means of improved two-level optimization method for discrete variables.Not only with stress and section size constraints it can be directly calculated, but also with stability and displacement constraints can it be dealt with by this method for the structural optimum design with discrete variables.Finally one example is analyzed, and the result shows that the presented method is accurate and efficient.