Acute-on-chronic liver failure is a serious acute liver function decompensation based on chronic liver diseases. It has an extremely high short-term mortality rate and has always been a research hotspot in the field of liver disease. In recent years, China, Asian Pacific Association for the Study of the Liver, and European Association for the Study of the Liver have issued or updated the diagnostic criteria for acute-on-chronic liver failure, but the diagnostic criteria vary greatly due to different etiologies and pathogeneses in the East and the West. Prognostic models have also been constantly updated based on different diagnostic criteria. This article compares the above diagnostic criteria and introduces the new prognostic models in detail, in order to improve the understanding and diagnosis/treatment of this disease among clinicians.