Mostly product design knowledge and experience exists in design handbook or expert's brain. During design process, designer has to refer to many handbooks and design materials, and design solution is hard to be reused. In order to deal with these deficiencies in digital design, this paper focuses on knowledge-reuse-oriented product modeling and knowledge management. Design knowledge is used to guide design process, and it is embedded into product model along with design process. Through analyzing design process, mechanical product knowledge is classified into four basic types that include calculation formula, design rule, engineering check and parameter spectrum etc. In order to manage and encapsulate design knowledge the concept of knowledge component(KCOM) is proposed. Design knowledge base can be organized as a hierarchy tree of KCOM. Knowledge reuse in KCOM level is the reuse of whole object in knowledge base, and knowledge reuse in item level is the reuse of basic knowledge type. Finally knowledge reuse approaches between knowledge base and CAD system is presented.