As population ageing has intensified intergenerational contradiction, the discourse power of the elderly in modern society has often been ignored or weakened. In this case, sustainable activities will become vital factors for helping the elderly rebuild their relationship with society. This research applies qualitative research methods, including extensive literature review and user interviews, for design iteration and reflection. The research problem involves how to make compelling connections amongst the lonely elderly, volunteer institutions, stakeholders, and the community through designing a sustainable service system. Overall, the process and results of this research are beneficial to the sustainable development of the social environment and intergenerational relations. The entire system design includes the design of platform, environment, and services; eventually, it evaluates sustainability from the system level of online and offline parallelism. It has preliminarily completed design positioning, intending to achieve the vision of synergy through future case studies and practical tests.