It is difficult for one enterprise to separately master all the knowledge related to its product innovation design. Aiming at this problem, open innovation is introduced to product design. Key technologies of product open innovation design based on knowledge are researched. Based on the ontology expression of internal innovation knowledge, external innovation knowledge and knowledge of innovation theory, open innovation design from function to structure is achieved by gradually indexing. Each functional structure is considered as a gene. Structure innovation design is optimized by cross evolution and variation evolution, achieving organic fusion internal and external innovative design knowledge.