As a unique product of China 's planned economy system, the unit system community is a basic social unit with the unit as the core for unified construction, the production relationship as the link, and the living and living service function as the main function. Its membership is relatively simple, mainly for unit workers and their relatives. Since the reform and opening up, China 's economic system has shifted from a planned economy to a market economy. As the dominant type of community in the planned economy period, the unit system community has slowly disintegrated in the process towards socialization and commercialization. With the disintegration of the unit system, the unit community has emerged as a community hybrid process characterized by the privatization of housing property rights and the complexity of community composition, and has gradually become a mixed community. In the process of community hybridization, the composition of the unit community population has gradually become complicated. Due to the different identity characteristics and identity differences among residents, their behavior patterns in the community space also show differentiation, which to some extent separates the community cohesion. The family courtyard of Chinese universities is a typical semi-decomposed unit community, and the elderly are one of the main users of community public space. From the perspective of identity theory, this research focuses on the behavioral differentiation of the elderly groups with different identities in the unit community in the community public space. Taking the family courtyard of a university in China as an example, through field investigation and observation and in-depth interviews, this research analyzes the location selection and aggregation behavior differentiation of the two types of elderly groups in the community public space. Through the grounded theory, the content of in-depth interviews is coded and analyzed to explore the influencing factors of the spatial behavior differentiation of the elderly groups in the unit community. The study found that ( 1 ) the elderly prefer sunny space activities in the community ; ( 2 ) The elderly groups with different identities have obvious behavioral differentiation in the public space, and this phenomenon will be improved during the period when children are active in the public space ; ( 3 ) The behavioral differentiation of the middle-aged and elderly groups in the family hospital of the university in the public space is mainly due to the differences in emotional identity, rights identity and cultural identity between the retired employees and the family members of the employees. Based on the research results, this paper puts forward some suggestions on the planning and design of public space in unit community, in order to promote the benign interaction of different identity groups in the community, enhance community cohesion, and provide reference for the renewal and construction of community public space. Keywords : unit community, public space, behavior differentiation, identity theory, social integration