In order to improve the efficiency of product design and reuse in heterogeneous system of knowledge sharing, this paper introduced the concept of ontology into product variant design, and grinding machine design was as an example. A lot of experience and accumulated knowledge in product design was shared and reused. It is precisely to formulate ontology knowledge such as variant design features and parameter, and applied the software protege4.3 to construct ontology model, as well as runed resoning on model data information. It developed a set of complete product intelligent system of variant design, which can effectively solve the problem of the repeated design and greatly shorten product development cycle.