As significant cultural carriers of regional historical development and sociocultural evolution, settlement toponyms preserve historical information about the natural environment, population migration, ethnic interactions, and social development in border areas. Particularly in multi-ethnic border regions, toponyms are not merely spatial identification symbols but also crucial materials for revealing changes in social structure, cultural transmission, and the formation of local identity. The Yanbian region, as a typical multi-ethnic border area in Northeast China, has long experienced the migration, development, and interaction of various ethnic groups including Han, Manchu, and Korean, resulting in a toponymic landscape characterized by multilingual and multicultural integration. Taking 2,570 settlement toponyms in the Yanbian region as research subjects, and employing methods such as mathematical statistics and GIS spatial analysis, this paper explores the formation mechanisms and spatial representations of multi-ethnic social formation in border areas from the perspective of toponymic culture. The findings are as follows:(1) The formation of settlement toponyms in Yanbian exhibits distinct historical stages. Since the Qing Dynasty, through processes of borderland development, population migration, ethnic interactions, and state governance, a multilingual toponymic system comprising Chinese, Korean, and Manchu toponyms gradually emerged and coexisted. This system records the historical processes of different ethnic groups entering the border area, developing the land, and undergoing social integration, reflecting the continuity and complexity of the formation of multi-ethnic society in the border region.(2) The spatial pattern of toponyms reflects the long-term adaptation of settlements to the natural environment. Different ethnic groups have formed differentiated settlement distribution characteristics based on their ecological environments and modes of production. Specifically, Korean settlements are mainly distributed in river valleys and plain areas, adapting to paddy rice farming; Han Chinese settlements are more widely distributed, with a relative concentration in higher-altitude areas, reflecting the influence of dryland farming and resource development activities; Manchu settlement toponyms show a decreasing distribution trend with increasing altitude, mainly concentrated in low-altitude river valleys and gentle terrains, indicating the adaptation of traditional settlements to water systems, forest resources, and diverse natural environments.(3) Toponyms related to production and livelihood, grassroots organizations, resource utilization, and human aspirations record the evolutionary processes of economic development, social governance, and cultural identity, revealing the composite characteristics of the multi-ethnic social formation in the Yanbian border area in terms of economic activities, social organization, and cultural psychology.By systematically examining settlement toponyms in the Yanbian region, this study reveals the formation mechanisms and spatial representations of multi-ethnic social formation in border areas, thereby expanding the research perspective of toponymic culture in serving the historical interpretation of border societies. As spatial and cultural materials that document socio-historical processes, toponyms carry multiple values such as ethnic migration, cultural transmission, and local identity, offering a new cognitive pathway for deepening research on the formation mechanisms of multi-ethnic border societies and for the preservation of regional cultural heritage.