Abstract: This research investigates the environmental characteristics of community parks and outdoor health behavior activities of the floating elderly in Shanghai, a typical city with the floating elderly gathering. Based on the health behavior characteristics of the floating elderly, it reveals three types of outdoor health behavior activities, which are the physical health behavior activity, psychological health behavior activity and social health behavior activity. Based on their environmental needs in the process of outdoor activities, it further proposes six types of environmental characteristics of community parks that affect outdoor activities, which are the overall coordination of activity space, the perfection of activity facilities, the accessibility of activity space, the safety of activity space, the comfort of activity space and the landscape aesthetics of activity space. It adopts the structural equation model (SEM) to analyze and test the spatial influences of six types of environmental characteristics on three types of outdoor health behavior activities of the floating elderly. Six types of environmental characteristics contain 24 environmental factors, and three types of outdoor health behavior activities contain nine activity factors. The results show that the physical health behavior activity and psychological health behavior activity are most affected by the comfort of activity space, while the social health behavior activity is most affected by the accessibility and safety of activity space. Through quantitative analysis of the spatial environment characteristics that affect the outdoor health behavior activities of the floating elderly in community parks, this research provides reference for the optimization design of green space in community parks.