Hepatitis B surface antigen quantification refers to the specific amount of the outer shell protein of the hepatitis B virus. The outer shell protein of the hepatitis B virus is not itself infectious, but it usually accompanies the hepatitis B virus. Therefore, the quantification of Hepatitis B Surface Antigen reflects the presence of Hepatitis B virus infection in the body, or the activity of Hepatitis B virus replication, and can also be used as a marker of Hepatitis B virus infection. The higher the level of hepatitis B surface antigen, the more active the hepatitis B virus replication. If the hepatitis B surface antigen count is low, it often indicates inactive hepatitis B virus replication. Patients with very low quantitative hepatitis B surface antigen, but who show indications for treatment, can often achieve better results with standardized antiviral therapy such as interferon. In the event of an abnormal hepatitis B surface antigen quantification, it is recommended to seek prompt medical attention, follow the doctor’s instructions for further examination, clarify the cause with the doctor’s help, and carry out targeted treatment or therapy.