Abstract: The optimization of first natural frequency of composite laminate was carried out in FEA software under Four-Edge-Simple-Support and Four-Edge-Fixing-Support boundary conditions, while the ply angles of every single layer of the laminate were confirmed as design variables. The result indicates that fundamental frequency under two boundary conditions is improved by 4.9% and 16.2%, respectively. The failure intensity of the structure before and after optimization was also analyzed comparatively. Then, the optimization method was applied in composite grid-structure aerofoil box of pilotless aircraft with the ply angles of 24 single layers of skin and ribs confirmed as design variables, and the results indicate that the fundamental frequency is improved by 10.6%. At the same time, the load capacity of the wing after optimization is improved to some degree.