Memory and identity form a dialectical unity of dynamic mutual construction. Innately neutral as an information carrier, memory acquires value orientations through acquired social experiences. It serves as the psychological foundation for individuals to form self-perception, distinguish the Other, and cultivate a sense of group belonging, endowing meaning to present life and prompting individual group identification. The expansion of group size breaks memory bonds built on direct personal experience. To consolidate collective identity, communities construct shared memory systems via historical narratives, cultural symbols, and rituals to transcend the temporal, spatial, and physiological limits of individual memory. Since memory naturally fades and easily triggers identity fractures, groups revitalize collective memories through daily symbolic infiltration and periodic rituals, creating a closed loop in which memory shapes identity while identity reshapes memory in return. Their mutually formative symbiosis reveals the spiritual mechanism behind social integration and the lasting survival of communities.