Abstract: Objective：To study the changes of regulatory B cells (Breg) subsets in peripheral blood of patients with idiopathic thrombocytopenic purpura (ITP) and related cytokines, analyze their correlation and explore the role of Breg in the pathogenesis of ITP. Methods：The proportional changes of CD19⁺B, CD5⁺CD19⁺B and CD1d^(hi)CD5⁺CD19⁺B subsets in peripheral blood were determined by flow cytometry (FCM) and the levels of IL-10 and TGF-β1 in the supernatant of culture medium of peripheral blood mononuclear cells (PBMC) were measured by ELISA in 30 patients with ITP and 30 matching healthy controls. Results：Compared to normal controls, the proportions of CD19⁺B, CD5⁺CD19⁺B subset were increased, but the proportion of CD1d^(hi)CD5⁺CD19⁺B subset was decreased, and there were statistically significant differences (P<0.05). The expression levels of IL-10 and TGF-β1 in culture medium of PBMC of ITP patients were lower than those in healthy controls (P<0.05). There was a positive correlation between the proportion of CD1d^(hi)CD5⁺CD19⁺B subsets and the levels of IL-10（r=0.717,P<0.05）, but there was no correlation between CD1d^(hi)CD5⁺CD19⁺B subsets and the levels of TGF-β1 (r=0.073, P>0.05). Conclusion：The low expression of CD1d^(hi)CD5⁺CD19⁺B subsets and related cytokines IL-10 may participate in the mechanism of immunoregulative dysfunction in ITP patients.