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, Treg cells Regulatory T cells played a negative role in immune. This study was aimed at investigating the changes of Treg cells frequency and function, and the expression of costimulatory molecules during Peg-IFN-αand nucleoside analog(ue) therapy.Meanwhile, the investigators wanted to verify whether Peg-IFN-α suppressed the virus, which led to the decline of Treg cells frequency and function;negative regulation of Tregs for immune cells diminished, hence, the function of immune cells recovered.