To study the product identity factors of equipment product form design based on sequential relationship. Based on the basic theory of product identity， metaphor and DIS（Design Information Structure）are used to extract the sequential product identity factors of equipment. The types of sequential product identity factors and its adaptability are studied. Then the extraction method， key features of sequential product identity factors is studied. An innovation method based on sequential product identity factors is proposed， which is further verified in the Zoomlion equipment styling project.