Faced with the reality of “a large base and diverse needs” of rural vulnerable children in China, as well as the limitations of the traditional single rescue model, exploring the professional service path led by social organizations has become an important topic in social work practice and research. Taking the vulnerable children assistance project in Qingshen County, Sichuan Province (supported by The Salvation Army) as a case, this study combines data collection methods such as questionnaires and observation to analyze the practical experience of the project over 5 years (from April 2020 to September 2025), and focuses on modeling the mechanism of multi-dimensional intervention of social organizations in services for rural vulnerable children. The research finds that: (1) The “social worker + volunteer” dual-linkage mechanism effectively integrates professional and social resources, enhancing service sustainability; (2) The “economic assistance + emotional companionship + development support” (three-in-one) service model systematically addresses the diverse needs of vulnerable children across the physical, mental, social, and spiritual dimensions; (3) Through the “3-S” service model—namely, “standardized identification of service objects, standardized management of volunteers, and systematic design of activities”—the project has cultivated local volunteer service teams and local social organizations, significantly enhancing the capacity to build the grass-roots child protection network. This research provides replicable practical experience of services for rural vulnerable children in underdeveloped areas by offering references for social organizations to participate in the child welfare cause.