Objective To investigate the change of T helper 17 cells (Th17) in the peripheral blood mononuclear cell (PBMC) in patients with liver cystic echinococcosis. Methods Fifty-six subjects were divided into three groups: healthy controls (HD, n = 20), patients with cystic echinococcosis (CE, n= 18) and patients with cystic echinococcosis combined with bile fistula (BF,n= 18). The frequency of Th17 cells in CD4+ T lymphocytes was detected by flow cytometry. Th17-related cytokines including interleukin (IL)-17 and IL-23 were measured by enzyme-linked immunosorbent assay (ELISA). The data were analyzed by t test and Pearson correlation analysis.Results The frequency of Th17 in the peripheral blood was significantly lower in CE group compared to BF group and HD group [(0. 23±0. 11)% vs (0. 76±0.43)% vs (0.52±0.50)%; t=2. 225 and4. 077 respectively, both P＜0.05), while there was no statistical difference between BF group and HD group (t=1. 931, P＞0.05). The levels IL-17 and IL-23 were (12.1±3.7) ng/L and (84.4±46.0) ng/L respectively in CE group, which were lower than those in BF group [(15.5±4.1) ng/L and (138.6±37. 9) ng/L, respectively; t=2. 515 and 3. 649 respectively, both P＜0.05] and those in HD group [(14.8±4.4) ng/L and (138.1±48. 7) ng/L, respectively; t=2. 401 and 3. 706 respectively,both P ＜0.05], while there was no statistical difference between BF group and HD group (t=0. 534,P ＞0.05). Serum concentrations of IL-17 were all positively correlated with the concentrations of IL23 in these three groups (r=0. 657, P＜0.05). Conclusion The frequeny of Th17 cells in PBMC and the serum concentrations of IL-17, IL-23 are significantly reduced in patients with cystic echinococcosis.