The host immunity has been generally recognized as the main factors to determine the outcome of chronic hepatitis B virus (HBV) infection. Previous studies have shown that HBV-specific T cell and B cell function are exhausted in chronic hepatitis B (CHB) patients. Interestingly, these impaired T and B cell functions could be partially restored by antiviral treatment, but this recovery seemed to be uncompleted even if long-term HBV suppression and HBeAg seroconversion. Recently, several emerging evidences have indicated that HBV-specific immune responses could be nearly recovered after hepatitis B surface antigen (HBsAg) seroconversion. This phenomenon suggest that HBsAg may play a key role in the immune tolerance or immune exhaustion. Indeed, our recent studies have found that the patients with HBsAg seroconversion display an HBV-specific T and B cell responses. Thus, the amount of HBsAg may serve as a possible mechanism for evading the host immune response, while anti-HBs antibody and HBV specific-T cell responses provide protective immunity.