Background Health inequality poses a challenge to improving the quality of life of older adults as well as the service system. The literature rarely explores the moderating role of medical services accessibility in the association between socioeconomic deprivation and health inequality. Objective This study examines the socioeconomic deprivation and medical services accessibility associated with health inequality among older Chinese adults, which will contribute to the medical policy reform. Methods Using data from the 2011, 2014, and 2018 waves of the Chinese Longitudinal Healthy Longevity Survey (CLHLS), we analyse 14,232 older adults. This paper uses a concentration index (CI) to measure the income-related health inequality among the target population and employs a recentered influence function–concentration index–ordinary least squares (RIF-CI-OLS) model to empirically analyse the correlation between socioeconomic deprivation and health inequality among older Chinese adults. Based on the correlation analysis, we discuss the moderating effect of medical services accessibility. Results We find that health inequality exists among older Chinese adults and that the relative deprivation in socioeconomic status (SES) is significantly associated with health inequality (β∈ [0.1109, 0.1909], P < 0.01). The correlation between socioeconomic deprivation and health inequality is moderated by medical services accessibility, which means that an increase in medical services accessibility can weaken the correlation between socioeconomic deprivation and health inequality. Conclusion China needs an in-depth reform of its medical services accessibility system to promote the equitable distribution of medical services resources, strengthen medical costs and quality management, and ultimately mitigate the SES reason for health inequality among older Chinese adults.