Hepatitis B surface antibody is a kind of protective antibody produced by the immune system after the surface antigen of hepatitis B virus stimulates the human body. Weakly positive HBsAb indicates that there is insufficient resistance to hepatitis B virus in the body, and there is still a possibility of infection with hepatitis B. After hepatitis B virus invades the human body, the immune system will produce substances to resist the virus. After the hepatitis B virus invades the human body, the immune system of the human body will produce substances to resist the virus. Hepatitis B surface antibody is precisely a kind of antibody produced by the immune system of the human body against the surface antigen of the hepatitis B virus, which can be combined with the surface antigen of the hepatitis B virus to neutralize the infectious power of the hepatitis B virus, and play a role in preventing the invasion of the hepatitis B virus into the human body. As long as the body’s immune system is strong enough to produce enough surface antibodies to neutralize the surface antigen, the hepatitis B virus that invades the body will be completely eliminated. The higher the titer of hepatitis B surface antibody in the serum, the stronger the protection of the body. Positive hepatitis B surface antibody alone indicates that the body has resistance, but if it is weakly positive, there are the following cases: non-specific reaction in normal people, after injection of hepatitis B vaccine or hepatitis B immune globulin and during labor and delivery when the antibody passes through the placenta into the baby’s body, all these cases can not effectively fight against the hepatitis B virus, and it is necessary to continue to receive hepatitis B vaccine to keep the antibody at a high titer level. Therefore, HBsAb is the protective antibody produced by the human immune system against the hepatitis B virus. Weakly positive HBsAb indicates that the body’s immunity is insufficient, and it is necessary to take the hepatitis B vaccine in order to effectively prevent hepatitis B infection.