The work aims to explore the construction method and design path of the airport terminal washroom service system with the Universal Design (UD) theory under the background of advocating for "integration of disabled and healthy individuals" and improving "social welfare". With Guangzhou Baiyun International Airport as an example, the user personas of airport washrooms were subdivided and redefined from the perspective of "user diversity", and a multidimensional user obstacle analysis framework covering three types:"long-term", "phased", and "situational" was developed. Subsequently, the "differentiated scenario" variable was added to observe and analyze the differences in user behavior and status in different fields, and design strategies were derived. Finally, a new and systematic airport washroom service process and touch points were constructed according to the service logic. The washroom service system constructed based on the universal design method that takes into account both "segmented users" and "differentiated scenarios" helps to provide effective, inclusive, and fair services for public transportation hubs with a large user base and complex types, such as airports.