AIM: To investigate the association between IL-10-producing regulatory B (B10) cells and the clinical features of thyroid-associated orbitopathy (TAO). METHODS: A total of 30 patients with TAO were recruited at Zhongshan Ophthalmic Center from May 2015 to December 2015. Peripheral blood mononuclear cells (PBMCs) were separated from blood samples of 30 TAO patients and 16 healthy controls and stimulated with CD40 ligand and CpG for 48h. The frequency of IL-10+ B cells was examined by flow cytometry and the correlation between the frequency of IL-10+ B cells and clinical features of TAO was analyzed by SPSS. RESULTS: The frequency of IL-10+ B cells among CD19+ B cells in TAO patients was significantly lower than in healthy controls (TAO: 4.66%±1.88% vs healthy control: 6.82%±2.40%, P<0.01). The frequency of IL-10+ B cells showed a positive correlation with disease activity of TAO measured by Clinical Activity Score (CAS) (r=0.50, P<0.01), and became higher in TAO patients with family history of Graves’ disease (GD) (P=0.04). CONCLUSION: The decrease of the frequency of IL-10+ B cells in TAO patients indicates the deficiency of B10 cells in TAO, and the positive association with disease activity suggests its important role in TAO inflammation regulation.