In this paper the effects of sympathectomy on T lymphocytes of irradiated mice were investigated. The whole blood sample was collected from mice irradiated with 0.5Gy, 3Gy and 6Gy and injected with 6-OHDA respectively. The number of T lymphocytes, T lymphocyte subsets and their activated cells were detected by flow cytometry. Results show that the thymus index of irradiated mice with sympathectomy obviously decline. And the number of T, Th and Tc/Ts cells collected from irradiated mice decrease with the increment of absorbed doses. The number of Th, Tc/Ts cells becomes obviously larger though the number of T cells of sympathectomized group is smaller than that of the group without sympathectomy at the same absorbed doses. Compared with the control group, the number of CD3,+, CD25,+, activated Th and Tc/Ts cells increase with the increment of absorbed doses while the parameter of the sympathectomized sample are larger than that of control group. All these indicate that the sympathetic nerve has a positive function to the immune function of irradiated mice.