Objective:Recently,selenium was used for the treatment of Graves disease. However,there has been no reports that selenium affected the immune function of Graves disease at the cellular level so far. It is reported the effect of sodium selenite on Treg cells in peripheral blood mononuclear cells in patients with Graves disease in the present study. Methods:AFS were used to detect the level of serum selenium;PBMC( Peripheral blood mononuclear cells) were extracted,then,cultured with sodium selenite. Foxp3 mRNA expression was tested by Real-time fluorescence PCR,and ELISA was used to detect the secretion of IL-35. Results:The serum sodium selenite levels of GD group are significantly lower than the HC group;The expression of Foxp3 mRNA and secretion of IL-35 are both increased. Conclusion:It shows sodium selenite could improve the state of immune disorders by recovering the function of Treg cells.