Abstract： Objective： To observe the clinical effect of modified Simiao Yong'an Decoction for hyperthyroid heart disease with dual deficiency of qi and yin complicated with phlegm blended with blood stasis syndrome. Methods：A total of 60 cases of patients with hyperthyroid heart disease were divided into the control group and the study group according to the random number table method， with 30 cases in each group. The control group was treated with routine western medicine， and the study group was additionally treated with modified Simiao Yong'an Decoction based on the treatment of the control group. The indexes of thyroid function， heart function， and blood lipid and traditional Chinese medicine(TCM) syndrome scores before and after treatment were compared between the two groups；the clinical effects and the incidence of adverse reactions in the two groups were evaluated. Results：The total effective rate in the study group was significantly higher than that in the control group(P＜0.05). After treatment，the levels of free triiodothyronine(FT3) and thyroxine(FT4) in the two groups were significantly decreased when compared with those before treatment(P＜0.05)， and the levels of thyroid- stimulating hormone(TSH) in serum were significantly increased(P＜0.05)； the improvement of thyroid function indexes in the study group was better than that in the control group(P＜0.05). After treatment， the left ventricular ejection fraction(LVEF) and the ratio of peak E to peak A(E/A) of mitral valve forward blood flow in the two groups were significantly increased when compared with those before treatment(P＜0.05)， and the levels of left ventricular end- diastolic diameter(LVEDD) and left ventricular end- systolic diameter(LVESD) were decreased(P＜0.05)；the improvement of heart function indexes in the study group was better than that in the control group(P＜0.05). After treatment， the levels of total cholesterol(TC)， triglyceride(TG) and lowdensity lipoprotein(LDL- C)， and TCM syndrome scores in the two groups were significantly decreased when compared with those before treatment(P＜0.05)，and the levels of high-density lipoprotein(HDL-C) were increased(P＜0.05)；the improvement of the above indexes in the study group was better than that in the control group(P＜0.05). There was no significant difference being found in the comparison of the incidence of adverse reactions between the two groups(P＞0.05). Conclusion： Modified Simiao Yong'an Decoction has a significant curative effect in the treatment of hyperthyroid heart disease， which can effectively improve the function of thyroid gland and heart in patients and reduce the levels of blood lipid， with high safety.