In this paper, we present a generative design method for supporting creative conceptual design in a multi-agent system. The hierarchical multi-agent system architecture offers a promising framework and an evolutionary computational approach provides a basis for supporting generative design in distributed environments. The evolutionary approach relies upon a tree structure rather than a known binary string in general GA (Genetic Algorithm). The system can generate simple 2D sketch shapes, which are generated by using general. Mathematical expressions and selected shapes are dealt with to form 3D components. These components are classified and saved in a SQL sever based database (component base). The complex design is implemented via combination of different components that come from the component base. The layout of components is generated by a genetic algorithm. The generative process is illustrated through an architectural design example.