Hepatitis B surface antigen quantification is one of the five quantifications of hepatitis B, and it is also the main one, its normal value is 0-1S/CO. If it is greater than 1S/CO, it indicates surface antigen positive, if it is less than 1S/CO, surface antigen is negative, its significance is to judge the indicator of antiviral treatment. When anti-hepatitis B virus treatment, the most common test is the quantification of hepatitis B virus DNA, but this test can drop below the detection line soon after the anti-viral treatment has achieved efficacy. If the test drops below the detection line, and if we continue to observe the efficacy of antiviral therapy, we need to look at the five quantitative hepatitis B tests, especially the change in surface antigen quantification, which can reflect the efficacy of antihepatitis B virus and the prognosis of antihepatitis B virus therapy.