Abstract: The 3D CAD kernel supports the development and application of large industrial software, and the open framework of 3D CAD kernel supports more roles to participate in CAD kernel development, optimization, and usage. Based on the analysis of mainstream 3D CAD kernels, we propose an open CAD kernels framework that supports multi-role collaborative development, including modules such as geometric representation, topological representation, discretization, and visualization. Key issues of the open framework, such as the object-oriented extension method of CAD main modules, the interoperability between modules and the customized development of applications based on CAD kernel, are discussed; The feasibility of the framework is verified by a customized pipeline-CAD application which is developed by extension of several modules of the framework.