Inequality of opportunity is the underlying reason behind the health inequality of the middle-aged and elderly in China. Promoting equal opportunities is also the focus of realizing health equity. Based on Roemer’ s theory, the research examines the effect of “circumstance” and “ effort” on the health of middle-aged and elderly people, and also measures and decomposes the degree of opportunity inequality by parametric estimation, Shapley and nonlinear Oaxaca-Blinder model. At last, the contribution of relative “effort” is further measured based on variance decomposition. The results show that, among the “circumstance” factors, children’s social-economic status, living in urban areas before the age of 16 and community environment have long-term positive effects on the health, while among the “ effort ” factors, education brings about the most significant influence.“Circumstance” has a bias effect on “ effort”, that is the better the children’ s socialeconomic status, the more chances to form better life habit and receive high education. The degree of opportunity inequality is 0. 105 where family economic conditions, parents ’ education and parents’ health at an early age are the main sources. The heterogeneity among gender, regional and birth cohort mainly derive from the influential difference of “circumstance” on health. After relative “effort” is listed, lifestyle and education account for 12.17% of total inequality. Therefore, focusing on the socio-economic environment of families during childhood and including poverty, education, and health care in health interventions from childhood is an important way to break down health inequalities.
