The aim of this study was to investigate the expression of Th17 cells and regulatory T (Treg) cells in peripheral blood of patients with immune thrombocytopenia (ITP) and to clarify the role of the Th17/Treg cell ratio imbalance in pathogenesis of ITP. Patients were divided into the pre-treatment group (active group) (n = 38) and post-treatment group (remission group) according to the platelet count and curative effect. Post-treatment group was further divided into remission group (n = 24), partial remission group (n = 10), and non-remission group (n = 4). 30 healthy subjects were enrolled in control group. Flow cytometry was used to detect the percentages of peripheral blood Th17 cells and Treg cells in CD4(+) T cells from ITP patients and controls respectively. The results showed that the percentages of Th17 cells in active group and non-remission group were significantly higher than those in control group (p < 0.05). The percentages of Th17 cells in remission group, partial-remission group were also higher than those in control group, but there were no statistically significant differences between these groups. The percentage of Th17 cells in remission group was lower than that in active group, but there was also no statistically difference between two groups. The percentages of Treg cells in active group, partial-remission group and non-remission group significantly decreased, compared with in control group (p < 0.01). The percentage of Treg cells in remission group was lower than that in control group, but there was no statistically significant difference. The ratio of peripheral blood Th17/Treg cells in active group, partial-remission group and non-remission group was higher, as compared with in control group. The ratio of peripheral blood Th17/Treg cells in remission group was higher than that in control group, but there was no statistically difference between two groups. It is concluded the percentage of Th17 cells and the ratio of Th17/Treg cells are higher in active group. The percentage of Treg cells is low in active group, partial remission and non-remission groups. The imbalance of Th17/Treg ratio may play a critical role in ITP pathogenesis.