This paper proposes a modular design method of Vacuum Coating Machine based on expert systems and case base. It builds a modular design system of Vacuum Coating Machine based on knowledge engineering. This paper discusses expert systems based on data base and CBR, and discusses Knowledge structure, the modular design method and the method of CBR. It searches for the most suitable type and configuration according to the basic design parameter, designs restriction and regulation. After calculation, it looks for type from expert systems, and then get the configuration from case base, then generates design specifications and BOM. This design solves the calculation and data sharing during problems on the vacuum coating machine design with CAD technology. And it realizes that structural design, process design, product data management integration.