There is no study that performs local buckling control analytically in composite box sections.. Because the elastic buckling coefficients required to determine the critical buckling stresses are unknown. Therefore, only strength control can be performed in the sections in question, or the cross-section dimensions can be determined according to strength. Suppose the subject is a thinwalled composite box section with a very high probability of buckling under an axial compression load. In that case, only the strength is insufficient, and buckling control should be considered. In this study presented to solve this problem, the ‘’Equivalent Homogeneous Section’’ method was developed for the first time by considering the critical buckling stresses. Studies were conducted to determine the most suitable optimum dimensions of the composite box section under the supervision of both strength and buckling conditions, and they were carried out on the specially created equivalent homogeneous box section. The assumption that optimum equivalent homogeneous and optimum original composite box sections are obtained by removing the insides of solid homogeneous and solid composite sections of the same dimensions to the maximum extent is accepted. The optimization problem is solved by creating functional relations between the variable parameters of the box sections and the buckling coefficients, minimizing the cross-sectional area and maximizing the removal ratio. When the original composite box cross-sectional area with the determined optimum dimensions is compared with the equivalent homogeneous box cross-sectional area, it is analytically determined that the savings obtained increase depending on the ratio of the elasticity modules of the materials forming the composite box section, and it is also verified with numerical examples.