Abstract: Studies have shown that the buckling resistance of composite sandwich structures can be effectively improved by reinforcing the surface layer with X-shaped carbon nanotubes (CNTs) distributed along the thickness direction. Adopting such a configuration will lead to sudden changes in the surface layer stiffness along the thickness direction, as well as sudden changes in displacement and stress. It is necessary to study the influence of the distribution configuration of CNTs along the thickness direction on the displacement and stress of the sandwich structures. Currently, there are few high-order models that can accurately analyze such problems. Thus, a high-performance theoretical model for functionally graded composites is developed. Based on the proposed model, analytical solution for the functionally graded sandwich beam is presented. By analyzing the bending behavior of typical sandwich structures, the performance of the proposed model is verified by comparing with the three-dimensional finite element results. Subsequently, the influence of distributing configuration of CNTs along thickness direction on displacements and stress of the sandwich structures is further investigated. Numerical results show that the proposed high-performance model can accurately predict the sudden change of displacements and stress of the carbon nanotubes reinforced sandwich structures.