Abstract: Carbon fiber reinforced composites have become important engineering materials in aerospace and other fields. However, the low efficiency of layup design and the complexity of layup design of traditional composites have resulted in a certain design strength redundancy and structural overweight of composite components. Double-Double, as a new composite ply method, has the advantages of simple ply design and convenient ply weight reduction, and has become the future development trend of ply design. This paper combines the Double-Double layup method, ABAQUS parametric modeling and strain energy theory to optimize the weight reduction of composite C-beam, and the established finite element analysis model can effectively show the bending force state of C-beam. Combining finite element analysis and test results, it is shown that the Double-Double members can effectively replace the traditional ply members, and the bending stiffness and ultimate load of the Double-Double C-beam are improved by 9.28% and 12.34%. For the two optimized variable thickness Double-Double C-beams, the bending stiffness and strength are not only not reduced, but their weights are also reduced by 12.5% and 17.5%, respectively, achieving the weight reduction optimization goal.