It is theoretically impossible for a normal person infected with the hepatitis B virus to be cured, i.e. it is impossible for the surface antigen of hepatitis B to turn negative. However, in clinical practice, we occasionally see individual patients with a negative hepatitis B virus surface antigen. Hepatitis B virus surface antigen conversion is usually seen in the following two situations. One is a true conversion, which usually occurs when the hepatitis B virus is completely cleared by the action of the own immune system while on antiviral therapy. In the other case, the hepatitis B virus enters a quiescent phase through clinical treatment that inhibits the replication of the virus, and the body develops immune tolerance to the hepatitis B virus, and the surface antigen of the hepatitis B virus is not detected and becomes negative.