The purpose of this paper is to build knowledge description model for complex product design. In order to uniform the semantic of glossary in design process, an extensive glossary semantic tree is built up and the corresponding semantic similarity calculation algorithm is proposed. The complex design knowledge can be divided into instance pattern, chart pattern, formula pattern and rule pattern. The knowledge models are proposed for these four pattern knowledge models. At last, a design knowledge modeling and reusing system for complex product is achieved, and the design knowledge can be inherited by it.