(2 ) taking the vehicle platform variant as precondition, this paper deeply researches the function-structure and function-structure decomposition of rear-axle . the rear-axle product model for variant design is built using general cad software ( unigraphics ) (2)以满足平台改型设计需求为前提,深入研究了汽车后桥的功能结构和功能结构分解,利用通用cad软件(unigraphics)建立了适应变型设计的汽车后桥产品模型。