Abstract: To avoid repetitive work in the design of serial products,a knowledge-based hierarchical model along with its realization framework is presented to facilitate parametric design.Different levels of sub-models and their interrelationships are discussed in detail,and some key measures,such as establishing design features to incorporate domain knowledge,using tri-tuple to uniformly describe domain knowledge,and applying knowledge to guide assembling processes are introduced.An example of designing power transmission gear system of mechanical press is provided to illustrate the realization of hierarchical model in practice.