Objective: To observe the quantity of Treg cells and Th17 cells in spleen of adult primary immune thrombocytopenic purpura (ITP) patients. Methods: 43 ITP cases with splenectomy treatment were enrolled from December 2008 to June 2016 at Union Hospital of Fujian Medical University, including 20 males and 23 females with a median age of 36 (18-76) years. The controls were thirty patients who underwent splenectomy because of pancreatic diseases or splenic impairment, including 21 males and 9 females with a median age of 47 (21-69) years. The quantity and ratio of Treg cells and Th17 cells were examined by immunohistochemistry between ITP patients and controls. Results: ①The quantity of Treg cells in ITP were less than controls[ (11.3±4.7) /mm² vs (59.0±15.0) /mm², t=-22.894, P<0.001], but Th17 cells were more than controls[ (235.2±69.4) /mm² vs (181.1±23.7) /mm², t=13.768, P<0.001]. So the ratio of Treg/Th17 in ITP was lower than controls (0.048±0.027 vs 0.328±0.086, t=19.522, P<0.001) . ② The quantity of Treg cells in cases without response after splenectomy were less than cases with response[ (9.5±5.0) /mm² vs (11.6±4.7) /mm², t=2.723, P=0.010], and there is no statistical differences between the two groups about the quantity of Th17 cells and the ratio of Treg/Th17 cells[ (232.3±80.8) /mm² vs (239.6±66.9) /mm², t=1.108, P=0.277; 0.040±0.024 vs 0.053±0.027, t=0.540, P=0.592]. Conclusions There is a significant difference about the quantity of Treg cells and Th17 cells in spleen between ITP patients and healthy controls, and they are relevant to the response after splenectomy.