Abstract: This work proposes a higher-order functionally graded theory. By comparing with the published results and three-dimensional finite element results, accuracy and efficiency of the proposed model have been verified. Through analyzing mechanical behaviors of the functionally graded structures, it is found that in-plane stiffness and bending stiffness of seal plate can be significantly improved by using a reasonable distributing profile of the CNTs. In addition, stiffness of the functionally graded structures can be further improved by improving the volume fraction of the CNTs. As a result, an accurate and efficient model has been presented for analysis of mechanical behaviors, which can serve for structural design of aircraft seal plate.