Objective To investigate the changes of peripheral blood Foxp3+ regulatory T cell (Treg cell) in patients with ovarian cancer (OC).Methods In 46 patients with OC and 46 normal controls,the percentage of peripheral blood CD4+ Foxp3+ Treg cell was assessed by flow cytometry and Foxp3 mRNA level was detected by real-time quantitative reverse transcription polymerase chain reaction.The level of plasma.transforming growth factor β1 (TGF-ββ 1) was measured by enzyme linked immunosorbent assay.Results The percentages of CD4+ Foxp3+ Treg cell,Foxp3 mRNA and level of plasma TGF-β1 in patients with OC were statistically higher than those in normal controls [(11.42 ± 2.67)％ vs.(8.94 ± 1.98)％,0.59 ± 0.21 vs.0.37 ±0.14,(35 580 ±7274) ng/L vs.(28 610 ±5631) ng/L,P=0.0000].Conclusion The number and/or function of CD4+ Foxp3+ Treg cell in peripheral blood of patients with OC are abnormal,CD4+ Foxp3+Treg cell may participate in the occurrence of OC.