Deep-ocean mining vehicle system has not only coupled relationship between component systems, but also a variety of design requirements of each system to accomplish the specified multi-tasks. To meet the multi-objectives of the complex system, multidisciplinary design optimization (MDO) is performed. Metamodels such as kriging model and response surface model are employed to reduce computational costs for MDO and to facilitate the automation and integration of component systems in a design framework. After verifying accuracies of metamodels, metamodel-based MDO for deep-ocean mining vehicle system is formulated and performed. Finally, results and advantages of the proposed design methodology are discussed.