Abstract: Objective To investigate the expression of FOXP3 and CD25 in CD4+ T cells of peripheral blood from patients of early new-onset systemic lupus erythematosus(SLE) before and after treatment. Methods Forty-four early new-onset SLE patients including twenty-four with active disease (SLEDAI≥10), twenty with low active disease (SLEDAI<5) were enrolled in this study. Twenty-one healthy volunteers were also included as controls. Peripheral blood samples before and after treatment were collected. Cell populations of CD4+CD25+T cells, CD4+CD25highT cells and CD4+FOXP3+T cells were quantified and the expression of CD25 in CD4+FOXP3+T cells and FOXP3 in CD4+CD25highT cells were also analyzed. Results Peripheral blood CD4+CD25+T cells and CD4+CD25highT cells in active new-onset lupus patients (3.95%~13.04%, 0.04%~1.34%) were significantly lower than in low active lupus patients (7.27%~24.48%, 0.14%~3.07%) (P<0.05,P<0.01); Though there was no significantly difference of CD4+FOXP3+T cells in active (7.46%~17.38%) and in low active (5.30%~23.00%) new-onset lupus patients, both were significantly higher than in normal controls(2.51%~12.94%) (P<0.01,P<0.01); CD25 expression in CD4+FOXP3+T cells in active lupus patients (25.24%~62.47%) was significantly lower than in low active untreated lupus patients(30.35%~75.25%) and normal controls(54.83%~86.38%) (P<0.05, P<0.05). Meanwhile, Mean fluorescent intensity (MFI) of FOXP3 in CD4+CD25highT cells from patients with new-onset SLE was significantly lower than from normal control（100.52~160.92 vs. 122.58~198.10., P=0.012）. CD4+CD25highT cells increased significantly in active lupus patients after corticosteroid treatment. Conclusions The disproportional expression between CD25high and FOXP3+ in CD4+T cells may play an important role in imbalance of immune homeostasis in new-onset patients with active SLE.