Antineoplastic drugs can suppress the immune system in the body and induce hepatitis B virus replication, making hepatitis B active, which may occur even in HBV DNA-negative patients with viral suppression phase infection. The relapse of chronic hepatitis B often leads to different degrees of liver damage, which makes chemotherapy and other treatments difficult. On the other hand, in HBV-infected patients undergoing oncologic chemotherapy, if abnormal liver function occurs, it is often difficult to distinguish whether the liver damage is caused by antitumor drugs or by hepatitis B relapse. After antiviral treatment, as long as the hepatitis B virus is well suppressed, the liver injury that occurs again must be caused by anti-tumor drugs. The doctor can stop the original drug and continue the treatment with other anti-tumor drugs.