Abstract: Objective To observe the effect of phosphorylated α-Syn on TH activity. Methods pLNCX2-S129D α-Syn vector was constructed using overlapping extension polymerase chain reaction (OE-PCR). The retroviral particles were packaged and infected MN9D cells. Expression of α-Syn in MN9D was tested using real time RT-PCR. Phosphorylated TH protein level was tested using Western blot. Results Sequences of wild-type and S129D α-Syn were both correct. The result of real time RT-PCR showed that wild-type and S129D α-Syn genes were overexpressed in MN9D compared with uninfected MN9D and vector control group. TH phosphorylation was reduced in wild-type α-Syn group, while increased significantly in S129D α-Syn group. Conclusion　α-Syn phosphorylation involves in regulation of TH activity in MN9D cells.