Data annotation is the foundation for the application of artificial intelligence (AI). This paper reviews the real-world applications of data annotation in public health and clinical medicine, with the aim of providing reference for promoting the construction of China′s smart medical system and the modernization of public health governance. The Chinese and English articles on the applications of data annotation in public health and clinical medicine were retrieved from the China National Knowledge Infrastructure (CNKI) and the Web of Science Core Collection with the time interval from January 1, 2020 to April 20, 2025. Data annotation demonstrates significant application potential in smart healthcare management and services, diagnostic assistance, disease surveillance, pharmacovigilance and new drug development, as well as chronic disease management. It substantially enhances the accuracy of medical AI models, optimizes clinical workflows, and advances precision medicine. Currently, medical data annotation shows the development trends of automation, multi-center collaboration, and dynamization, while still facing challenges such as inconsistent standards and privacy protection. In the future, it is necessary to build a standardized and intelligent annotation ecosystem to fully release the potential of AI in the medical field and help achieve the Healthy China initiative.