This paper discusses the application of CAD / CAE integrated design to the fuselage airproof main frame, builds up a CAD structure model and a FEA model. Simultaneously all the main parameters are determined according to the environment of fuselage airproof main frame and the design requirements in analyzing the rigidity and strength. The structural strength and flexural rigidity of the fuselage main frame are computed and verified by CAE system software and the results are analyzed.