Abstract：Objective：To observe the clinical effect of Tangmin prescription based on syndrome differentiation for patients with type 2 diabetes mellitus with dual deficiency of qi and yin syndrome and its effect on insulin sensitivity. Methods：A total of 61 cases of patients with type 2 diabetes mellitus with dual deficiency of qi and yin syndrome were divided into the control group and the treatment group according to randomized controlled trials，30 and 31 cases in each group respectively. Both groups were given diet and exercise control；the control group was treated with metformin tablets，and the treatment group was treated with Tangmin prescription combined with metformin tablets. After eight-week treatment，the changes in fasting blood glucose(FBG)， postprandial 2- hour blood glucose(P2hBG)， hemoglobin A1c(HbA1c)， fasting insulin(FINS)， insulin sensitivity index(ISI)， Homeostasis model assessment of insulin resistance(HOMA- IR) and curative effect of Chinese medicine syndromes in the two groups were compared. Results：The total effective rate of Chinese medicine syndromes was 87.10% in the treatment group，better than that of 50.00% in the control group(P＜0.05). After treatment，the indexes of FBG， P2hBG， HbA1c， FINS， ISI and HOMA- IR in the two groups were improved when compared with those before treatment(P ＜ 0.05) ， and the improvement of P2hBG，FINS，ISI，HOMA-IR and Chinese medicine syndrome scores in the treatment group was more significant(P＜0.05). Conclusion：For patients with type 2 diabetes mellitus with dual deficiency of qi and yin syndrome，the therapy of Tangmin prescription combined with metformin tablets has better curative effect than that of simple metformin tablets. It can effectively reduce their P2hBG，improve insulin resistance and insulin sensitivity，which has significant curative effect in improving Chinese medicine symptoms.