In architectural design, designers often need to consider a variety of factors in the full life cycle. As these factors are usually hidden in the final results of the detailed design (architectural design drawings, etc.), it brings greater difficulties for the reuse of the architectural design knowledge. This paper presents a new concept "Affordance" based on the design methodology to solve the problem in modeling and application of the tacit design knowledge in architectural design. Firstly, this paper will explore the concept "Affordance"which is mainly used in the conceptual design at present and aplly to the detailed design stage of architectural design. Secondly, the information model based on Form-Behavior-Affordance (FBA) is built so that designers can model the whole hidden factors in the final results of the full life cycle. Thirdly, the Genetic-Programming technology is used to model the architectural knowledge. At last, a case of expanding a school building is used to present the feasibility of the method proposed in this article.