The understanding of spatial inequality in health care services is critical for reasonable policy-making and management. In this study, we present a novel approach to analyze the demand-supply of health care services using taxi data. Taxi data provide observations of individual travel activities, and hence can be used to characterize the actual demand-supply of health care services. We apply the proposed approach in Guangzhou, China to carry out a case study. The resultsshow the spatial disparities in health care service access. About 21.05% of the total population has high hospital accessibility, while the remaining 78.95% has relatively low hospital accessibility (i.e., roughly an "80/20" distribution). It is found that 6.29% of the population lives in high-density suburban communities but has relatively low hospital accessibility. Most of the hospitals serve a population that is compatible with their capacity. One hospital is found to have a small capacity but to serve a large population, while two hospitals have relatively high capacities but serve small populations. These findings can help improve our understanding of spatial inequalities in public service provision, and may also provide useful information to address the health care problems of an aging population in contemporary, rapidly urbanizing China.