With the growing trend of population mobility and the aging process in China, a significant number of accompanying elderly migrants have moved to major cities. However, in community public spaces, the behavioral differences between caregiver-oriented elderly migrants (CO-AEMs), family reunion-motivated elderly migrants (FR-AEMs), and local elderly residents hinder social interactions between these groups. This study aims to explore opportunities for cross-group social interaction within the community environment. By utilizing GPS data collection and activity log analysis, along with spatiotemporal behavioral research methods, this study reconstructs the spatiotemporal trajectories of three groups of elderly individuals. The study proposes a social interaction potential (SIP) model based on the “support-constraint” framework. Through qualitative analysis of spatiotemporal behavioral characteristics and quantitative measurement of the degree of spatiotemporal behavioral co-occurrence across four modes, this study reveals the differentiated impact mechanisms of spatial and behavioral factors on social interactions, ultimately assessing SIP in differentiated community spaces and activities. This research highlights differences across spatial, behavioral, and temporal dimensions that hinder social interactions between the groups. Spatial and behavioral differences are primarily attributable to the lifestyle habits and activity preferences of the elderly, while temporal discrepancies reflect varying degrees of family-related constraints across the different groups. Furthermore, informal community public spaces show higher SIP than formal facilities. Additionally, the similarity in behaviors across groups facilitates social interactions. FR-AEMs and local elderly residents show higher SIP in self-care behaviors, while CO-AEMs and local elderly residents demonstrate stronger SIP in behaviors related to their family and grandchildren. Based on the segmented assimilation theory, this study proposes hierarchical community governance and spatial optimization strategies for activities and spaces with different SIP. The aim is to cultivate opportunities for interaction while respecting the characteristics of accompanying elderly migrants and to foster the construction of an inclusive community environment. The findings provide theoretical support and practical pathways for community space planning and social governance in the context of an aging society.