Objective To observe the effect of celastrol on the secretion of interleukin (IL)-17 in peripheral blood mononuclear cells in patients with sympathetic ophthalmia (SO), and its possible mechanisms. Methods Venous blood samples were extracted from 10 cases of sympathetic ophthalmia patients and 10 health objectives. The peripheral blood mononuclear cells (PBMCs) were isolated by density gradient centrifugation and then were divided into 4 groups. Group A (control group): PBMCs of health objectives; Group B: PBMCs of SO patients; Group C: PBMCs of SO patients with 0.5 μmol/L celastrol in the medium; Group D: PBMCs of SO patients with 1 μmol/L celastrol in the medium. After culturing the cells for 3 days, the supernatant of 4 groups was collected, and the levels of IL-23 and IL-17 were detected by enzyme-linked immuno sorbent assay (ELISA). Then, the 50 ng/ml rIL-23 was added into the medium of group A which was the group A1; the 50ng/ml rIL-23 and 1 μmol/L Cela were added into to the medium of group A which was the group A2. For the medium of group B, the 50 ng/ml rIL-23 was added into the medium which was the group B1; the 50 ng/ml rIL-23 and 1 μmol/L celastrol were added into to the medium of group B which was the group B2. After culturing for 3 days, the supernatant of cells of these 4 groups was collected, and the levels of IL-17 were detected by ELISA. Results In group A, the levels of IL-23 and IL-17 were (228.43±17.27) pg/ml and (220.55±31.15) pg/ml respectively. In group B, the levels of IL-23 and IL-17 were (513.85±36.46) pg/ml and (866.77±72.92) pg/ml respectively. In group C, the levels of IL-23 and IL-17 were (381.07±20.93) pg/ml and (517.43±54.87) pg/ml respectively. In group D, the levels of IL-23 and IL-17 were (237.14±17.97) pg/ml and (242.89±34.09) pg/ml respectively. Between group A and D, there was no statistically significant difference in IL-23 or IL-17 level (P＞0.05); but when comparing other groups, the differences were statistically significant (P＜0.05). The levels of IL-17 in group A1 and group A2 were (428.43±24.53) pg/ml and (229.15±23.28) pg/ml and the difference was statistically significant (P＜0.05). The levels of IL-17 in group B1 and group B2 were (1373.39±89.51) pg/ml and (571.01±94.88) pg/ml and the difference was statistically significant (P＜0.05). Conclusion Celastrol can inhibit the secretion of IL-17 by PBMCs in SO patients via inhibiting the secretion of IL-23.