BACKGROUND: China has made remarkable progress in scaling up essential services during the last six decades, making health care increasingly available in rural areas. This was partly achieved through the building of a three-tier health system in the 1950s, established as a linked network with health service facilities at county, township and village level, to extend services to the whole population. METHODS: We developed a Theory of Change to chart the policy context, contents and mechanisms that may have facilitated the establishment of the three-tier health service delivery system in rural China. We systematically synthesized the best available evidence on how China achieved universal access to essential services in resource-scarce rural settings, with a particular emphasis on the experiences learned before the 1980s, when the country suffered a particularly acute lack of resources. RESULTS: The search identified only three peered-reviewed articles that fit our criteria for scientific rigor. We therefore drew extensively on government policy documents, and triangulated them with other publications and key informant interviews. We found that China's three-tier health service delivery system was established in response to acute health challenges, including high fertility and mortality rates. Health system resources were extremely low in view of the needs and insufficient to extend access to even basic care. With strong political commitment to rural health and a "health-for-all" policy vision underlying implementation, a three-tier health service delivery model connecting villages, townships and counties was quickly established. We identified several factors that contributed to the success of the three-tier system in China: a realistic health human resource development strategy, use of mass campaigns as a vehicle to increase demand, an innovative financing mechanisms, public-private partnership models in the early stages of scale up, and an integrated approach to service delivery. An implementation process involving gradual adaptation and incorporation of the lessons learnt was also essential. CONCLUSIONS: China's 60 year experience in establishing a de-professionalized, community-based, health service delivery model that is economically feasible, institutionally and culturally appropriate mechanism can be useful to other low- and middle-income countries (LMICs) seeking to extend essential services. Lessons can be drawn from both reform content and from its implementation pathway, identifying the political, institutional and contextual factors shaping the three-tier delivery model over time.