Functional cure of hepatitis B refers to chronic hepatitis B that has been treated with antiviral therapy and has achieved negative hepatitis B surface antigen, produced hepatitis B surface antibody or not produced hepatitis B surface antibody, undetectable hepatitis B virus DNA, normal liver biochemistry and improved liver histological examination by liver aspiration, and remains unchanged after stopping treatment. Although functional cure of hepatitis B has been achieved, hepatitis B virus still exists in the nucleus of liver cells and there is still a risk of hepatocellular carcinoma, so regular review and observation are still needed. It is also important to note that patients who have achieved functional cure may have reactivation of hepatitis B virus during the application of chemotherapy or immunosuppressive drugs and may have relapse.