Abstract: Objective:To detect frequency of and programmed cell death-1(PD-1) expression of CD4⁺CD25^highTreg peripheral blood of systemic lupus erythematosus(SLE) patients and to explore their roles in immune disorder of SLE. Methods:Flow cytometry(FCM) was used to determine the frequencies of peripheral blood CD4⁺CD25^highTreg and CD4⁺CD25^lowT cells and the PD-1 expression on these cells in SLE patients and healthy normal controls. Results:The frequency of CD4⁺CD25^highTreg among CD4⁺Treg in peripheral blood of SLE patients group(0.63±0.31)% decreased significantly(P<0.01),compared with normal control group(2.07±0.74)%. The PD-1 expression on CD4⁺CD25^highTreg in SLE group(24.99±18.65)% was obviously higher than that in normal control groups(6.97±1.92)% (P<0.05). There were also was no significant differences in both the frequency of CD4⁺CD25^lowT cells and the PD-1 expression on these subset cells among two groups(P<0.05). Conclusions:Decreased number of CD4⁺CD25^highTreg and upregulated expression of PD-1 on these Treg may play an important role in the pathogenesis of SLE.