Abstract： Objective： To observe the clinical effect of Xiaoying tang combined with methimazole for hyperthyroidism (HPY) in plateau area and its effect on the level of thyroid hormones. Methods： A total of 80 cases of HPY patients were randomly divided into the control group and the treatment group， 40 cases in each group. The control group was given methimazole，and the treatment group was additionally given self-made Xiaoying tang based on the treatment of the control group. Both groups were treated for eight weeks. The clinical effect，and the changes in the levels of total triiodothyronine (TT3)， total thyroxine(TT4)， free triiodothyronine(FT3)， free thyroxine(FT4)， thyroid stimulating hormone(TSH) in serum as well as syndrome scores before and after treatment were observed and compared between the two groups. Results：The total effective rate was 97.50% in the treatment group and 80.00% in the control group，the difference being significant(P＜ 0.05). After treatment，when compared with those before treatment，the levels of TT3，TT4，FT3 and FT4 in serum in the two groups were decreased(P＜0.05)，and the levels of TSH were increased(P＜0.05)；the improvement of above each index in the treatment group was more significant than that in the control group(P＜0.05). After treatment， Chinese medicine syndrome scores in the two groups were significantly decreased when compared with those before treatment(P＜0.05)，and syndrome scores in the treatment group were significantly lower than those in the control group(P＜0.05). Conclusion：The therapy of Xiaoying tang combined with methimazole in treating HPY has definite clinical effect，which can significantly relieve patients'clinical symptoms，effectively regulate the level of thyroid hormones.