BACKGROUND:Health equity is a multidimensional concept that has been internationally considered as an essential element for health system development. However, our understanding about the root causes of health equity is limited. In this study, we investigated the historical roots and seminal works of research on health equity. METHODS:Health equity-related publications were identified and downloaded from the Web of Science database (n = 67,739, up to 31 October 2018). Their cited references (n = 2,521,782) were analyzed through Reference Publication Year Spectroscopy (RPYS), which detected the historical roots and important works on health equity and quantified their impact in terms of referencing frequency. RESULTS:A total of 17 pronounced peaks and 31 seminal works were identified. The first publication on health equity appeared in 1966. But the first cited reference can be traced back to 1801. Most seminal works were conducted by researchers from the US (19, 61.3%), the UK (7, 22.6%) and the Netherlands (3, 9.7%). Research on health equity experienced three important historical stages: origins (1800-1965), formative (1966-1991) and development and expansion (1991-2018). The ideology of health equity was endorsed by the international society through the World Health Organization (1946) declaration based on the foundational works of Chadwick (1842), Engels (1945), Durkheim (1897) and Du Bois (1899). The concept of health equity originated from the disciplines of public health, sociology and political economics and has been a major research area of social epidemiology since the early nineteenth century. Studies on health equity evolved from evidence gathering to the identification of cost-effective policies and governmental interventions. CONCLUSION:The development of research on health equity is shaped by multiple disciplines, which has contributed to the emergence of a new stream of social epidemiology and political epidemiology. Past studies must be interpreted in light of their historical contexts. Further studies are needed to explore the causal pathways between the social determinants of health and health inequalities.