Acute kidney injury (AKI) is a clinical syndrome with an acute decline or loss of glomerular filtration function caused by different reasons. It is an important disease affecting human health. In recent years, the incidence and mortality of AKI are rising continuously. Researchers both in China and other countries have performed many studies on the epidemiology of AKI. However, due to the difference in diagnostic criteria, diagnostic indicators, patient population, geographical location, and observation timing, the obtained data are quite different. In the early years, there were few studies on AKI epidemiology in China, and many of them reported single-center and small-sample data. The reported incidence of AKI is significantly lower than that in developed countries. In recent years, great progress has been made in the epidemiological research of AKI in inpatients and ICU patients. In this article, we review the current status of epidemiology of AKI in various clinical settings, aiming to explore its incidence and severity.