The importance of cam contour curve and the necessity of cam reverse engineering are discussed. The error sources during the course of cam reverse design are analyzed. The growth form innovative design method is researched, especially product structure growth form design method. The information of structure, dimension and tolerance should be perfected gradually during the course of growth form innovative design, and finally perfected when the product structure is finished, furthermore, using the current structure, dimension and tolerance information to conduct evaluation and control in the grow direction during the design process, to achieve the ultimate purpose of optimization design. Taken the innovative design of an precision cam as an example, the reconstruction of product structure and the product prototype reverse design are finished, and then the product is innovative designed. A practical designs technical ways based on growth form innovative design is systemly provided.