This chapter develops a conceptual framework for the sustainable regeneration of China’s old communities. A systematic review of 341 articles shows that social sustainability, anchored in resident satisfaction and quality of life, now defines the direction of community regeneration. This chapter positions densification as a central design tool. By strengthening land use, housing, infrastructure, and cultural functions, densification can boost vitality and long-term sustainability. The framework employs mixed-method evaluation, combining big and small data to capture resident needs. It ulimately argues that people-centered, socially sustainable regeneration offers the most inclusive path for upgrading China’s aging urban fabric.