Hepatitis B virus DNA quantification is one of the tests for chronic viral hepatitis B. It is a serological test used to detect the amount of hepatitis B virus in the blood, and thus an indicator of whether it is infectious. Hepatitis B virus DNA is the most basic core substance of hepatitis B virus and the basis of virus replication, and is the most direct, specific and sensitive indicator of hepatitis B virus infection. Positive hepatitis B virus DNA indicates the presence of hepatitis B virus replication in the body, and higher levels indicate stronger virus replication and greater infectiousness. To control the progression of hepatitis B, it is necessary to inhibit the replication of the hepatitis B virus. Hepatitis B virus DNA testing is reported in two ways: ① qualitative: that is, to determine whether it is negative or positive, and its normal value is negative; ② quantitative: that is, to detect the amount of hepatitis B virus in the blood. For HBeAg-positive chronic hepatitis B patients, when their serum DNA of hepatitis B virus is > 1x10E5copies/ml and their transaminases are elevated more than twice the normal value, they should start antiviral therapy; the gradual decrease and negative transformation of hepatitis B virus DNA is a sign to judge the effectiveness of antiviral therapy, during the treatment, if the hepatitis B virus DNA changes from negative to positive, it means Viral resistance has occurred and it is necessary to add or switch to other antiviral drugs. Therefore, the DNA of hepatitis B virus has a certain guiding significance for the judgment of the patient’s treatment result and the formulation of the treatment plan.