Abstract: Nowadays 2D CAD System has stood in a steady process as a highly standardized and intelligent tool for design and drafting, nicely provides interoperability and scalability. In this paper, the software architecture and data structure of 2D CAD System pertaining to a native 3D Solid Modeling System is discussed and analyzed. The software architecture of most popular 2D CAD System on market is implanted adaptively into the native 2D system to inherit most of its commonly accepted techniques.