Background. Regulatory B cells (Breg) are a distinct B cell subset with immunoregulatory properties. Pivotal to Breg function is interleukin-10. This study was to investigate the role of IL-10-producing B cell (B10) and its association with Treg and Th17 subsets in immune thrombocytopenia (ITP) patients. Methods. Peripheral blood mononuclear cells from ITP patients and controls were stimulated with PMA, ionomycin, and Brefeldin A. The frequencies of CD19+IL-10+ B cells, CD3+CD4+IL-17+ Th17 cells, and CD4+CD25hiFoxp3+ Treg cells were analyzed by flow cytometry. The mRNA expression of Foxp3 and RORγt was detected by real-time quantitative PCR. Results. The number of B10 cells was elevated in ITP patients. After first-line therapies, it remained at high level in patients who achieved complete or partial response but decreased in those who acquired no response. There was a positive correlation between B10 cells and Tregs in ITP both before and after therapies. The ratio of Treg/Th17 decreased in ITP, and it strongly correlated with B10 cells. Conclusions. The frequency of B10 cells is elevated in ITP and it correlates with both the Tregs counts and the Treg/Th17 ratio. B10 cells to regulate functional T cell subsets might be impaired in patients with ITP.