The work aims to propose a product design evaluation method that integrates the flow theory, AHP hierarchical analysis and fuzzy comprehensive evaluation method, so as to provide public fitness service facilities that strengthen user stickiness and form an incentive cycle, and improve users' concentration in using them. Firstly, the design requirements of public fitness facilities under each stage of the flow theory were refined, and an evaluation index system of design elements in the flow stage was constructed. The AHP hierarchical analysis method was used to conduct qualitative and quantitative analysis, and a comprehensive weight ranking with objectivity was calculated and tested, according to which the ranking results guided the design practice of intelligent fitness facilities for rowing machines. Finally, the fuzzy comprehensive evaluation method was used to evaluate and validate the design, to obtain the best design solution and to make improvements. After systematic research and analysis, a theoretical approach to product design evaluation combining the flow theory, AHP hierarchical analysis and fuzzy comprehensive evaluation method was designed, and the feasibility of the theoretical research method was verified with the smart rowing machine as an example. The theoretical combined product design method is helpful for the design guidance and scheme evaluation of public fitness service facilities, which can help fitness users to obtain the optimal fitness experience and provide theoretical reference for similar product design.