Three-dimensional rapid design for mechanical products is of great importance in machinery industry. In order to enhance market competitiveness, rapid design method of case-based reasoning has been imported. This paper discusses the meaning and system of rapid design, provides a case library built up based on parametric design and knowledge base, and probes the transformation technology from three-dimensional parameterized model to two-dimensional engineering drawing with optimized view position, view scale, and drawing note position in terms of geometry, dimension and engineering restriction. The final drawing accorded with the enterprise production demand. It can greatly shorten design cycle for mechanical products, and provides a new approach for the enterprise to quickly respond to market demands.