A modular design idea oriented to client customization is proposed to achieve product diversification and personalization. The Key technology of customized design is studied to meet the market's requirement of short cycle, high quality and low cost in product design and manufacturing. In the detailed design stage, the method of Top Basic Skeleton (TBS) is applied, which improves the rapid response ability of product design and shortens the product development cycle. On this base, a rapid design method of customized vacuum casting machine is illuminated. In the dynamic and changing market environment, the rapid design method plays an important role in improving the competitive power of enterprise.