The design system can be seen as the environment where design projects (product or system design, i.e. reengineering of whole or part or the enterprise) take place. The aim of this paper is to optimise the synchronisation and coordination of the development of several design projects in an environment with limited resources (material, human, know-how, etc.) and therefore satisfy the strategic performance objectives of the enterprise (cost, quality, flexibility, lead time, deadlines, etc.). With this intention, this paper deals with the extension of the GRAI methodology to model simultaneously the engineering of a design system and the engineering of an enterprise, seen as a complex system. Such a representation leads to define the role of the reengineering in enterprises industrial strategies, in order to answer the question: “how consider the design system, which is at the origin of this reengineering ?”. The main objective of this paper is therefore to use the double modelling (enterprise – design system) to identify the relations between the product and system design and the continual improvement process of an enterprise, in order to improve the global performance of this enterprise.