Abstract: In this paper, the dimension transfer method is presented in order to judge the mutual influence relationship between dimensions in the process of product variant design. The dimension constraint tree is defined with the parts dimension as node, and the size constraint relation is subdivided into mathematics constraint relation and structural constraint relation in detail. On the basis of the dimension constraint tree, an out-degree and in-degree dimensions set is constructed; meanwhile, according to different constraint relations, the dimension transformation rate and importance ranking in the set are analyzed by using dimension variant probability method and DEMATEL method so as to aggregate the variant design requirements on a few related dimensions. Finally, a case study is used to verify the proposed methods.