The training of children's fine hand movements plays an important role in their cognitive development. With scissors for children as the research object, the work aims to summarize the product design method and process oriented to the physiological and cognitive characteristics and behavioral habits of school-age children through the study of children's behavior in using scissors, so as to improve the children's experience in using scissors and promoting the development of children's fine hand movements and cognitive abilities. Firstly, the children's cognitive and fine hand movement development characteristics were analyzed by age group, and secondly, the behavior of children aged 6-8 years old using scissors was recorded by non-participant observation method, and the SAPAD model was used to map the three dimensions of "behavior-object-meaning". The meaning behind the user's behavior was clustered and analyzed and a meaning model was constructed and translated into core design elements to guide the scissor design. Finally, combined with the fuzzy comprehensive evaluation method, the product usability was tested to determine the optimal design solution. By analyzing the behavior of children aged 6-8 years old using scissors, a meaning model was constructed and four core design elements and two core components were obtained. Through product usability test, the design solution that met the physiological and cognitive development and behavioral characteristics of children best was preferably selected. A product design research methodology based on SAPAD user behavior study and incorporating school-age children's cognitive and physiological developmental characteristics can effectively enhance children's experience in operating scissors and promote their physiological and cognitive development. The study can also provide a new theoretical path and practical reference for the design and development of other similar products.