This paper addresses a design support method based on a recommendation algorithm of a subsystem converted from old design information to new design. The area of subsystem calculated considering constraints inside product, and is easy to replace from a template model which represents past product information. Based on a network model which represents design parameters and internal dependencies, proposed system generates scalable candidates of subsystem automatically based on cut-set calculation of a network structure. An independency which means easiness of the transplantation of a subsystem is evaluated using DEMATEL method. A proto-type system is developed and applied for design example of the OTEC (Ocean Thermal Energy Conversion) system.