 The most important method to slow down and stop the liver disease progression in patients with chronic hepatitis B is antiviral therapy, by which to achieve maintaining viral response during treatment or obtain sustained viral response after treatment. The aim of the therapy with interferon is make patients obtain immune control to HBV, in clinical practice, it was expressed as HBeAg seroconversion, HBsAg loss and sustained viral response in HBeAg positive patients. However, those targets cant be get in most patients by 48 weeks of interferon treatment, and some patients need extended treatment to enhance the rate of HBeAg seroconversion and HBsAg loss. In this cohort study, the efficacies of extended therapy of interferon in HBeAg positive chronic hepatitis B patients will be evaluated. 