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, CD8+T cells are the main effector cells in adaptive immune response. This study was aimed at investigating the changes of CD8+T cells frequency and function, and the expression of costimulatory molecules during Peg-IFN-αand nucleoside analog(ue) therapy.Meanwhile, the investigators want to verify whether Peg-IFN-α suppressed the virus and the reduction of virus led to the recovery of CD8+T cells function, or Peg IFN - alpha enhanced CD8+T cells function which gave rise to the decline of the virus.