They studied the knowledge sharing and reuse framework based on 3D geometric model, but did not answer the question of how to integrate and fuse design knowledge with 3D geometric model. Furthermore, their research object is 3D geometric model, thus the methods studied cannot be fully applicable to MBD model. The integration and fusion of design knowledge and product model will be more complicated in a MBD circumstances, because the MBD model contains more kinds of product information than 3D geometric model and the relationship between information is more complex. Therefore, this paper studies the integration and fusion of design knowledge and product model under the MBD methodology environment. Facing all types of design knowledge such as design intent, design justification, design decision and design option, a new product definition model, namely a 3D interpreted model is proposed, which integrates and fuses product geometric information, technical information and design knowledge. At the same time, the expression and construction methods of the 3D interpreted model are studied to form a complete method system. In order to verify the effectiveness of the proposed model and method, this paper develops the corresponding 3D interpreted model construction tool based on CATIA, and takes the MBD model in NIST MBE PMI validation and performance testing project [8] as the tool input. After the 3D interpreted model is constructed, the 3D interpreted model is stored in the graph database Neo4j. The main contribution of the proposed method is summarized as the following two aspects: (1) the proposed 3D interpreted model contains more extensive and fine-grained design knowledge, which not only explains the product geometric information, but also supports the explanation of roughness, tolerance and other technical information; (2) on the basis of improving the existing 3D model knowledge annotation method, the construction method of the 3D interpretation model network is proposed. The 3D interpreted model is expressed as a form that can be directly recognized and processed by computer, so as to promote the automatic and intelligent application of the 3D interpreted model. The objective of this paper is to form a new product definition model and its systematic theoretical methods. The new product definition model can explain and interpret the product geometric and technical information at the same time, and contains the design knowledge that completely describes the design process. It is of great significance to further improve the quality of product model and support the sharing and reuse based on product model. At the same time, systematic theoretical methods can guide engineers to carry out specific 3D interpreted model construction and expression. The rest of the paper is organized as follows: Section 2 gives the related research of MBD methodology and design knowledge classification and representation. Section 3 discusses the definition, connotation and expression of 3D interpreted model. Section 4 presents the construction method of 3D interpreted model. Section 5 presents a case study to verify the proposed method and Section 6 analyzes the experimental results. Section 7 gives the conclusion and future work.