An innovation method for conceptual design of mechanical products was proposed,combining the theory of inventive problem solving (TRIZ) with extension innovation method,and a conceptual design process model was established based on both.By establishing user requirement primitive model and conjugate analysis,the correlation between product requirements and functions was determined,the product function decomposition tree was established,the root conflict was obtained;then the original understanding corresponding to the engineering parameter query was extracted by using TRIZ tool set,multiple concept solutions were generated by the topologically transformable transformation.Finally the solutions were quantitatively evaluated and preferred by using the superiority evaluation method.The innovative design of the system was carried out with a small pipeline dredging robot as an example,and the practicality and effectiveness of the method were verified.