HBV-DNA and HCV-RNA are the core components of the virus and are the most direct, specific and sensitive indicators of viral infection. In acute hepatitis B, HBV-DNA positivity for more than 8 weeks can become chronic. In chronic infection, HBV-DNA can be instantiated into hepatocyte DNA, called integrated HBV-DNA, which is difficult to reach with therapeutic drugs if the HBV viral gene has been integrated into the host gene, which is one of the important reasons why HBV is not easily removed from the body. The use of fluorescence quantitative PCR method to detect viral genes can be both qualitative and quantitative, and its clinical application price are: ( 1 ) disease assessment: hepatitis virus replication in hepatocytes in large quantities is the initiating factor for immune damage of hepatocytes. The high level of serum HBV-DNA or HCV-RNA correlates with the degree of liver pathological damage, and the higher the level of HBV-DNA or HCV-RNA, the more severe the inflammatory response of liver tissue. Accordingly, the liver damage of patients with chronic hepatitis can be indirectly assessed by quantitative detection of HBV-DNA or HCV-RNA content. ( 2 ) Efficacy observation: The higher the level of viral genes before treatment, the worse the efficacy; the lower the level, the greater the possibility of virus clearance. Accordingly, the faster the level of viral genes decreases during the treatment process, the greater the chance of complete cure. Therefore, hepatitis virus genetic testing can be used as a means to predict and observe the efficacy of antiviral therapy. (3) Prognosis judgment: 1) treated or untreated chronic viral hepatitis, the prognosis of those with stable high viral gene levels is poor; 2) those infected with hepatitis virus by vertical transmission route, with high viral gene levels, low response to various antiviral treatments, and poor prognosis; 3) those with frequent fluctuations in viral gene levels during the course of the disease, despite normal other indicators reflecting liver cell damage, are prone to develop cirrhosis. ( 4 ) efficacy verification: any kind of antiviral drugs, liver function or hepatitis virus immune markers to evaluate its efficacy, are not sensitive and timely, if the fluorescence quantitative PCR method to detect the degree of suppression of viral replication, that is, the level of viral genes to evaluate the efficacy, is more ideal.