Abstract: Flow is a new concept in modern TRIZ theory, and flow analysis is a tool for systematic analysis of problems based on flow formation. However, formal research is insufficient and is difficult to be applied to intelligent design. Based on the elementary theory of extenics, a formal research on flow and flow analysis is conducted. It takes the material flow in the technical system as the research object, and uses elementary and composite elements to formally express the objects, behaviors, functions and other elements involved in the flow. Based on the structure and other elements, the extension flow model is established, and then the beneficial flow or the harmful flow is identified according to the flow analysis method. Finally, taking a company’s charging power supply production process defect as an example, the method is used to establish an extension flow model and identify the beneficial flow and the harmful flow. This research lays a good foundation for further obtaining extension knowledge research to improve defect flow.