The patients with chronic hepatitis B and achieved HBsAg level≤100 IU/ml after completed interferon treatment will be enrolled and observed for 96 weeks. Serum HBV DNA, HBsAg, anti-HBs, HBeAg, and anti-HBe will be measured every 3 months during the observation period, liver function tests were performed every 3 months also. The liver ultrasonic examination would be taken every 3-6 months. The primary endpoint is HBV DNA reaction. The secondary endpoints is HBsAg loss.