The work aims to study the optimization design strategy for the comfort of the elderly-oriented outdoor fitness facilities with the grounded theory. Through in-depth interviews and data collation, Nvivo 12 software was used to carry out qualitative research and analysis to clarify the comfort influencing factors of elderly-oriented outdoor fitness facilities. Then, data were collected by questionnaire survey and SPSS 26 software was used to analyze the reliability and validity to prove the rationality of the theoretical model of comfort influencing factors of the elderly-oriented outdoor fitness facilities. Finally, the comfort optimization design strategy of the elderly-oriented outdoor fitness facilities was proposed and applied to the design practice of the elderly-oriented outdoor fitness facilities. Behavioral comfort, psychological comfort and perceived comfort were the core categories of the theoretical model of comfort influencing factors of the elderly-oriented outdoor fitness facilities. The research results show that the research method based on the grounded theory has positive practical value in improving the comfort of elderly-oriented outdoor fitness facilities.