The trend of large-scale development of design industry requires efficient and full use of the rich design resources in the distributed multi-disciplinary resource environment. However, the designers are susceptible to many subjective and objective impacts, like knowledge structure, computing capability, geographic position, and administrative division. These impacts make the usage of design resources unstable and inefficient. Therefore, this paper proposed a computer-assisted automatic conceptual design system (CACDS). This system assumes that the design resources in the distributed multi-disciplinary resource environment exist in the form of functional elements with the same format, so that, the geographic, administrative, and disciplinary barriers in the design process can be broken, and the design resources can be fully used. CACDS is based on a group of basic concepts and their representations, its core is a functional solution generating algorithm, which is used to automatically generate functional solutions. As the result of the conceptual design, these functional solutions are also the starting point of the following detail design phase. Finally, a lighting system for underground greenhouse is designed as an illustrative case to validate the feasibility of the proposed CACDS.