Background The role of family doctors has become more and more important as people's demand for healthcare increases. However, there are still some problems in the implementation of family doctor contracting service, such as the difficulty of finding suitable family doctors and the difficulty of data sharing. Objective Develop a GIS-based Family Doctor Contract Service WeChat Mini Program (hereinafter referred to as the WeChat Mini Program), and complete the usability evaluation to provide residents with a faster and more efficient family doctor contracting service, and for the promotion of the application of mHealth technology in family doctor contracting service. Methods From January to June in 2022 through literature review to understand the residents' demand for family doctor contracting service and the development of WeChat applet; on-site survey of 200 community residents using random sampling method to analyze the residents' demand for WeChat applet; focusing on the design ideas and function orientation of WeChat applet, four focus group interviews were conducted with the residents, family doctors, administrators, and technicians; based on the demand analysis and the development elements, the development elements of WeChat applet were constructed. Four focus group interviews were conducted; based on the demand analysis and design ideas, the development elements of the WeChat applet were constructed. From June to August in 2022, a field survey was conducted on 96 users of the WeChat Mini Program using the System Usability Scale (SUS). Additionally, usability evaluation of the WeChat Mini Program was performed through key informant interviews and expert consultations. Results The main needs of residents for WeChat applets included health consultation (78.00%), quick location of nearby family doctors (75.00%), and health science popularization (71.50%). The design scheme of the WeChat applet covered the core functions of path planning and navigation, information query and display, residents' health management, online contracting and renewal, and online consultation; after the trial operation of the WeChat applet, the usability analysis was conducted, and the average score of SUS was (78.62±9.23), suggesting that the WeChat applet was practically operable and easy to learn. Conclusion The connotation of family doctor contracting service based on the GIS platform and the use of multifaceted thinking can ensure the scientificity and usability of WeChat applet development.