Objective To study and explore the effect of Total Glucosides of Paeony Capsules on the regulatory T cells（Treg） of autoimmune thyroiditis（AIT） model rats. Methods Forty SD rats aged 4～5 weeks were divided into blank control group， model group， total glucosides of paeony， selenium yeast group， 10 rats in each group， model group， white group（PTg） was injected subcutaneously into the pituitary gland glycosides group and selenium yeast， and AIT model was induced by high iodine water feeding. At the same time， the total glucosides of paeoniflorin group and the selenium yeast group were respectively treated with total glucosides of paeony and selenium yeast physiological saline solution After 6 weeks， the rats were sacrificed and the levels of serum TSH， TGAb and TPOAb were measured by enzyme-linked immunosorbent assay（ELISA） Proposed according to the acronym requirements specification， flow cytometry rat spleen CD4+CD25+Foxp3+Treg cell ratio. Results The levels of TSH， TGAb and TPOAb in model group were significantly higher than those in blank group. The total glucosinolate and selenium in paeony were lower than those in model group， and the indexes in paeoniflorin were lower than those in selenium group（P<0.05）. The proportion of CD4+CD25+Foxp3+Treg in spleen of rats in model group was lower than that of blank control group， the total glucosinolate and selenium of paeony was higher than that of model group（P<0.05） There was no significant difference between the groups of total glucosides of paeony and selenium（P>0.05）. Conclusion Total Glucosides of Paeony Capsules can reduce the level of TSH， TGAb and TPOAb in AIT rats， and improve the immune imbalance， which may be related to the function of increasing the proportion of CD4+CD25+Foxp3+Treg.