 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 defined as sustained viral response after treatment, however, most patients cant get this target after 48 weeks of interferon treatment, and some patients need extended treatment in clinical practice to enhance the rate of sustained viral response or HBsAg loss occurred during treatment. In this cohort study, the efficacy of extended therapy of interferon in HBeAg negative chronic hepatitis B patients will be evaluated. 