Pegylated interferon α-2a(Peg-IFN-α) not only inhibit viral replication, but also play an important role in immune regulation, while Nucleoside analog(ue) drugs only inhibit viral replication. In hepatitis B infection, NKs are the main effector cells in early antiviral innate immune response. This study was aimed at investigating the changes of NKs frequency and function, and the expression of costimulatory molecules during Peg-IFN-αand nucleoside analog(ue) therapy.Meanwhile, investigators want to verify whether Peg IFN - alpha suppressed the virus and the reduction of virus led to the recovery of NKs function, or Peg IFN - alpha enhanced NKs function which gave rise to the decline of the virus.