After entering the cell, the hepatitis B virus releases relaxed DNA (rcDNA) by shedding its capsid and enters the nucleus, where the positive strand is further extended by the action of DNA polymutase to form covalent closed-loop DNA (cccDNA). With cccDNA as the template, the pre-genomic RNA and mRNA for translation of various viral proteins are transcribed in the nucleus, and the post-transcriptional template remains intact and exists in the nucleus all the time, and the cccDNA is always present if the infected hepatocytes are not cleared, so the existence of HBV cccDNA is the most fundamental reason for the persistence of chronic hepatitis B virus and its difficulty of clearance. After chronic hepatitis B virus infection, the viral components that we can detect from the blood are HBV DNA, HBeAg and HBsAg. Among these components, the level of HBV DNA content in the blood depends on the replication of the intracellular virus and the rate of clearance of the virus in the peripheral blood, and does not correlate with the degree of clearance of intracellular cccDNA and the degree of clearance of virus-infected cells during antiviral therapy parallel to the degree of clearance of intracellular cccDNA and viral infected cells during antiviral therapy. Although the degree of clearance of virus-infected cells can be reflected in the decrease of HBeAg levels in blood, the level of HBeAg in blood does not necessarily parallel the level of cccDNA in the liver or hepatocytes because mutations in the pre-C region of HBV can lead to HbeAg-negative virus-producing strains. hbsAg, as the major component of viral outer membrane protein, is expressed during the replication of the virus 90% of the outer membrane protein is in excess and does not assemble into viral particles, for the presence of tubular particles and small spherical particles, the number of these outer membrane protein particles is more than 1000 times the number of viral particles, making it the most important component for serological detection after HBV infection, the level of HBsAg in blood was correlated with the level of HBV in the liver (r=0.43, P=0.028) and the level of cccDNA (r=0.54, P=0.004) in parallel.