Variant design is an important way for applying rapid response engineering. To meet the demand of the variant design of the product structure, a framework-based structure variant design method was proposed. The basis framework, as the most important concept of this method, represents the main function, structure and geometry characteristics of the components with the same function but different structure. This method unifies the formalization of heterogeneous variant parts. By the succession of the same basis framework, the replacement the different parts and the dimensional variant of the parts themselves, this method can realize the structure variant design and dimension variant design. The key basis framework modeling methods and technologies were discussed. Finally, the structure variant design software was developed on Pro/Engineer platform and the application proved the effectiveness of this method. 