Execution procedure and feature of CO/RSA is analyzed and building method of RSA is introduced. In this paper, multidisciplinary models of stratospheric airship are built and the coupled information in subsystem analysis is supplied by the RSA. In addition, the system optimization model and three subsystems, including aerodynamic/propulsion, structure, and energy subsystem, are discussed in detail. The design object is to find a feasible airship based on CO/RSA, which is with minimum total mass and satisfies the constrains including three balances: the balance between the energy supply and the energy requirement, the balance between mass and buoyancy, and the balance between drag ant thrust. The optimization result verified the rationality of MDO and CO/RSA in stratospheric airship’s conceptual design. Moreover, a reference of stratospheric airship program demonstration and design is provided.