This paper begins with the presentation of a service classification with two dimensions – continuity of coproduction and mutual adaptability, which define the four-category service systems served as a new reference architecture of service system design. The purpose of iDesign is to propose semi-automated value coproduction and systematic service innovation through the system awareness of ecological symbiosis. Namely, this paper proposes a methodology for service system design based on the symbiosis concepts, and the four-category service systems are characterised by the benefit-exchange properties of symbiosis (among the interactions and relationships between providers and customers during value coproduction). Meanwhile, this paper outlines a service performance evaluation model (in consideration of service productivity and customer satisfaction) and subsequently specifies the goal performance criteria as required for the four-category service systems. Finally, three artwork design service systems are used to exemplify the ideas behind the methodology of symbiosis-based service system design.