This kit is used for quantitative detection of hepatitis B virus surface antibody in human serum or plasma in vitro. Hepatitis B virus surface antibody (anti HBS) usually appears after the body is infected with HBV or vaccinated with hepatitis B vaccine. It has protective immunity to hepatitis B virus and is called a protective antibody. Anti HBS positive indicates that the disease is recovering or has previously been infected with HBV. It can not be used as the only index for the evaluation of patients' condition, but also for the comprehensive analysis of patients' clinical performance and other laboratory tests.