Objective To explore the role of Treg/Th17 cell ratio imbalance in the pathogenesis of idiopathic thrombocytopenic purpura (ITP) patients with different Traditional Chinese Medicine (TCM) syndrome differentiation classifications: bleeding due to blood-heat, Yin deficiency with fire hyperactivity and Qi deficiency-caused bleeding. Methods A total of 92 patients were divided into the bleeding due to blood-heat group (n=30), Yin deficiency with fire hyperactivity group (n=31) and Qi deficiency-caused bleeding group (n=31) according to the TCM syndrome differentiation classification. The peripheral blood samples were obtained from the patients and 30 volunteers served as healthy controls. The percentages of Treg cells and Th17 cells in the blood samples were analyzed by flow cytometry, and the mRNA levels of Foxp3 and ROR-γt were analyzed by RT-PCR. Results The percentages of Treg cells in the peripheral blood of 3 different TCM syndrome ITP groups were significantly lower than those of control group (P<0.05), that of the bleeding due to blood-heat group was significantly lower than that of Yin deficiency with fire hyperactivity group and Qi deficiency-caused bleeding group (P<0.05), and that of Qi deficiency-caused bleeding group was signficantly lower than that of Yin deficiency with fire hyperactivity group (P<0.05). The percentages of Th17 cells in peripheral blood of 3 different TCM syndrome ITP groups were significantly higher than that of control group(P<0.05), and that of Yin deficiency with fire hyperactivity group was signficanlty higher than that of Qi deficiency-caused bleeding group (P<0.05). The ratios of Treg/Th17 of the 3 different TCM syndrome ITP groups were significantly lower than that of control group (P<0.05), that of the bleeding due to blood-heat group was significantly lower than that of Qi deficiency-caused bleeding group and Yin deficiency with fire hyperactivity group (P<0.05), and that of Qi deficiency-caused bleeding group was significantly lower than that of Yin deficiency with fire hyperactivity group (P<0.05). The Foxp3 mRNA levels of 3 different TCM syndrome ITP groups were significantly lower than that of control group (P<0.05), and there were significant differences between each two groups by the pairwise comparison (P<0.05). While ROR-γ mRNA levels of the 3 different TCM syndrome ITP groups were significantly higher than that of the control group (P<0.01). Conclusion The decreased Treg cells in patients with ITP contributes to the development and progression of ITP. The imbalance of Treg/Th17 ratio may play a critical role in the pathogenesis of ITP. The distribution of the percentages of Treg cells, the ratio of Treg/Th17 and the mRNA level of Foxp3 in a increasing order is: bleeding due to blood-heat group < Qi deficiency-caused bleeding group < Yin deficiency with fire hyperactivity group.