Rapid urban population growth, especially in the last three decades, has begun to present a serious threat to living conditions, and posing increased risks to human health. Investigating the relationship between population size of city areas and self-rated health (SRH) can, we argue, provide insights for the management of population growth and improving SRH. This study employed a multilevel analysis to reveal the effects of city size on SRH both from migrant status and household registration perspectives, using data from the Chinese General Social Survey (CGSS) for 2013. The results indicate that an inverted U-shaped relationship exists between city size and SRH. Income and population density were shown to constitute significant positive impact drivers in relation to SRH. In contrast, migrant status and household registration exerted a significant negative effect on SRH. While the SRH status of migrants was not influenced by city size, city size was found to influence the SRH of individuals differently in different regions (i.e., eastern, central, and western parts of China). The results will be helpful in understanding the effect of the dynamics of city size on SRH in China, and will assist the Chinese government in employing effective strategies to improve SRH status.2 of 15 structure for the development of smaller cities. The scaling relationships between population and supercreative employment per MSA (Metropolitan Statistical Area) in 2003 for the US is superlinear (in which the exponent β = 1.15 > 1), and the scaling relationships between population and total wages per MSA in 2004 for US is superlinear (in which the exponent β = 1.12 > 1), too. It means that increasing population size will be returned by innovation, information, or wealth [8]. Dwellers' needs would impact on urban planning. For example, the city will plan parks, cycle paths, and squares due to citizens enjoying walking or using bikes than using cars. Therefore, more people may need more infrastructure [9]. However, the expansion of cities does not only result in benefits, it also has effects that include, among other things, increased consumption of resources, greater variation in living conditions, environmental pollution, car congestion, scarcity of public services, and a close proximity of living spaces that can lead to increased risks to human health [10][11][12][13][14][15]. For example, a study demonstrated that city size has a negative relation to individual happiness, exacerbating mental problems and reducing human health, and the pollution peaks always occur in large cities [2,16]. Researchers use the US as an empirical case to identify the difference of happiness status between urban and rural areas. The results show that the happiness increases outward from large central cities to small-town or rural areas due to the difference of size, density, and heterogeneity between urban and rural areas [17]. The findings of other studies also confirm this statement. For example, researchers utilized population size, xnorcsiz, and srcbelt t...