Adefovir, a purine derivative, is a new class of acyclic nucleotide antiviral drugs (acyclic nucleotide phosphate derivatives). The drug is phosphorylated by cellular enzymes to form a product with antiviral activity (adefovir diphosphate). Its mechanism of action against hepatitis B virus is to compete with deoxyadenosine triphosphate to terminate the extension of the viral DNA chain, thereby inhibiting the transcriptase activity of hepatitis B virus, inhibiting viral replication and exerting antiviral effects. Adefovir treatment for chronic hepatitis B can effectively inhibit HBVDNA, promote ALT normalization and improve liver histology with obvious clinical effects, but without the synergistic effect of other “external forces”, it is still very difficult and rare to achieve complete clearance of the virus and achieve the goal of radical treatment (HBsAg negative and/or HBsAg serological conversion). It is very difficult and rare to achieve true complete clearance of the virus to achieve eradication (HBsAg negative and/or HBsAg serological conversion). The reason is that adefovir does not have a direct killing effect on hepatitis B virus, nor does it remove and inhibit hepatitis B virus cccDNA. our patient took adefovir capsules before and after treatment for more than 4.5 years (including treatment after relapse in the middle of discontinuation) and achieved satisfactory results, with HBsAg negative and HBsAg serological conversion. The reason for this we think may be on the one hand the antiviral effect of adefovir capsules, the patient is more sensitive to adefovir, taking about six months, HBVDNA is negative, peripheral blood HBsAg titer also decreased significantly. On the other hand, the patient’s organism autoimmunity was activated, producing the effect of organism immunity to clear the virus. After 3 years of treatment, the patient discontinued the drug after stabilization and relapsed severely after 3 months. The relapse may have also activated the autoimmune function of the patient’s organism, and the combined effect of the activation of the organism’s autoimmune function and the antiviral effect of adefovir capsules led to the clearance of HBVDNA and the negative conversion of HBsAg and HBsAg serology. Clinically, the application of adefovir and other nucleoside (acid) analogues in the treatment of chronic hepatitis B. Whether the real cause of HBsAg negative and HBsAg serological conversion in individual patients is the coincidence of autoimmune clearance of the organism, or the antiviral effect of antiviral drugs or the result of the combined effect of both, needs further investigation. When can nucleoside analogue antiviral drugs such as adefovir treat chronic hepatitis B with negative HBsAg and/or HBsAg serological conversion and when can treatment be stopped? There is no unanimous opinion among domestic and foreign experts. In this case, after more than 14 months of treatment with adefovir capsules, despite the negative conversion of HBsAg and serological conversion of HBsAg, the level of anti-HBs in the serum is low. In order to consolidate the efficacy and prevent relapse, we believe that we still need to continue to adhere to antiviral therapy and review the level of anti-HBs regularly. If the level of anti-HBs can reach a high level, such as anti-HBs level of 100 mIU/mL or more, we can consider stopping the drug for observation.