To find the best program for solving contradiction in product innovation design,an extension design method was proposed,which had features of clear design goal,orderly conflict resolution process,satisfactory output program in product innovation design application.Through the analysis and comparison of common conflict resolution methods in innovative product design such as Theory of Inventive Problem Solving (TRIZ),rule/case-based reasoning,constraint loosening,negotiation,backtracking and extension design,the extension design method was chiefly characterized by its formalization,modeling and combination of qualitative and quantitative It was a modem design method that intelligently processed design objects,design systems and design processes.The formation of extenics and extension design,their relationship,the research methods and design principles of extension design were systematically introduced.The research status of various steps and links in extension design was summarized.The current deficiencies as well as future directions and ideas of extension design were discussed.Extension design methods and the strategy generating systems for their computer implementation were explained.A brief introduction was given to several typical software systems for extension design,and the prospective research objectives as well as difficulties were forecasted.