Background and Aim: Health is viewed as a form of human capital and a necessary basis for people to realize capabilities. Moreover, socioeconomic inequality in health outcome widens income inequality and exacerbates social inequality. The aim of this study is to measure socioeconomic inequality in health outcomes among the elderly in China. Methods: The data used in this study were sourced from China Health and Retirement Longitudinal Study in 2015, including 5643 participants aged 60 and above. Concentration curve and concentration index were applied to measure the extent of socioeconomic inequality in health outcomes among older adults. Furthermore, the decomposition method of concentration index proposed by Wagstaff was employed to quantify each determinant's contribution to the measured socioeconomic inequality in health outcomes. Results: The concentration index of Activity of Daily Living Scale and Center of Epidemiological Survey-Depression Scale score were -0.0064 and -0.0158, respectively, indicating pro-rich inequality in physical and mental health among the elderly. The decomposition analysis revealed that household income (41.15%), aged 70-79 (17.37%), being male (8.38%), and living in urban area (5.78%) were key factors to explain the pro-rich inequality in physical health. Furthermore, the results also suggested that household income (68.41%), being male (17.55%), having junior high school education (10.67%), and living in urban area (6.49%) were key factors to explain the pro-rich inequality in mental health. Conclusion: This study revealed that there are pro-rich inequalities in physical and mental health among the elderly in China, and the degree of pro-rich inequality in mental health is higher than that in physical health. Moreover, the results also suggested that household income is the biggest contributor to socioeconomic inequality in physical and mental health. Furthermore, this study found that educational attainment makes a substantial contribution to socioeconomic inequality in health outcomes, while the contribution of health insurance to health inequality is limited.