Abstract: The high flexibility in the structural design of carbon fiber-reinforced composites introduces complexity in optimization, making the reduction of computational costs while maintaining accuracy a significant research challenge. In this study, for the layup design of aerospace hat-stiffened composite structures, laminate parameter theory is combined with the newly proposed Double-Double layup method. By incorporating buckling theory, a functional relationship between optimization variables and objectives is established, enabling the optimization of the load-bearing capacity of hat-stiffeners and hat-stiffened composite laminates, effectively lowering computational costs. Axial compression tests are conducted to validate the theoretical model and the global optimization capability of the laminate parameters. Additionally, the buckling instability behavior of hat-stiffened composite laminates under axial compression is analyzed to provide further insights into their structural performance.