In 2006, the United States developed ISO 16792-2006 Technical product documentation-Digital product definition data practices adopted from the ASME Y14.41-2003 Digital product definition data practices. It was then revised and improved continuously. This standard is the basic standard for the three-dimensional digital design, which specifies how to add attributes, annotations, and other information to the design model to achieve a digital definition of the product. However, we believe that the way of modelling as well as the sequence and general requirements of modelling are of equal importance for reflecting design intent properly. Therefore, we propose a new international standard work item proposal to stipulate the construction, application and management requirements for the design model in the three-dimensional digital design process of mechanical products, which expressed as follows: 1) General requirements, including terms and definitions related to three-dimensional modelling, classification and composition of three-dimensional digital model, the naming principle of three-dimensional model files, definition and classification of geometric modelling features; 2) General process and requirements for part modelling, including common parts and specific parts, such as polymorphic parts, flexible parts and others; 3) General process and requirements for assembly modelling, including assembly level definition, assembly constraint definition, management of assembly structure tree, assembly model packaging and other requirements; 4) Model application management requirements, including basic requirements for model checking, model release, model data management, and the technical status management.