In the era of stock renewal, improving public service facilities has become the focus of micro-regeneration of old communities. The problems such as land shortage, low allocation of public facilities and unremarkable urban cultural characteristics in old mountainous city space have long restricted the regeneration and development of old city. The design of community complex with efficient utilization of stock resources can be an effective way to solve the above problems. This paper takes the Shuitu cinema and its surrounding land in Shuitu Town of Chongqing as the design research object, and proposes a composite design method for public facilities under high-density built environment through the analysis of site history evolution, daily life needs, traffic system and other aspects. Specifically, it includes composite function design based on compact development, urban texture protection based on historical resources, and traffic system reconstruction based on landscape pattern, in order to provide ideas for fully revitalizing the stock resources in the process of micro-regeneration of the old mountain communities.