Objective: To evaluate the long-term clinical effect of Tangyiping Granules(糖异平颗粒, TYP) on patients with impaired glucose tolerance(IGT) to achieve normal glucose tolerance(NGT) and hence preventing them from conversion to diabetes mellitus(DM). Methods: In total, 127 participants with IGT were randomly assigned to the control(63 cases, 3 lost to follow-up) and treatment groups(64 cases, 4 lost to follow-up) according to the random number table. The control group received lifestyle intervention alone, while the patients in the treatment group took orally 10 g of TYP twice daily in addition to lifestyle intervention for 12 weeks. The rates of patients achieving NGT or experiencing conversion to DM as main outcome measure were observed at 3, 12, and 24 months after TYP treatment. The secondary outcome measures included fasting plasma glucose(FPG), 2-h postprandial plasma glucose(2h PG), glycosylated hemoglobin(Hb A1c), fasting insulin(FINS), 2-h insulin(2hI NS), homeostatic model assessment of insulin resistance(HOMA-IR), blood lipid and patients’ complains of Chinese medicine(CM) symptoms before and after treatment. Results: A higher proportion of the treatment group achieved NGT compared with the control group after 3-, 12- and 24-month follow-up(75.00% vs. 43.33%, 58.33% vs. 35.00%, 46.67% vs. 26.67%, respectively, P<0.05). The IGT to DM conversion rate of the treatment group was significantly lower than that of the control group at the end of 24-month follow-up(16.67% vs. 31.67%, P<0.05). Before treatment, FPG, 2h PG, Hb A1 c, FINS, 2h INS, HOMA-IR, triglyceride(TG), total cholesterol, low- and high-density lipoprotein cholesterol levels had no statistical difference between the two groups(P>0.05). After treatment, the 2hP G, HbA 1c, HOMA-IR, and TG levels of the treatment group decreased significantly compared with those of the control group(P<0.05). CM symptoms such as exhaustion, irritability, chest tightness and breathless, spontaneous sweating, constipation, and dark thick and greasy tongue were significantly improved in the treatment group as compared with the control group(P<0.05). No severe adverse events occurred. Conclusion: TYP administered at the IGT stage with a disciplined lifestyle delayed IGT developing into type 2 DM. Objective: To evaluate the long-term clinical effect of Tangyiping Granules (on TYP) on impaired glucose tolerance (IGT) to achieve normal glucose tolerance (NGT) and therefore prevented them from conversion to diabetes mellitus (DM) . Methods: In total, 127 participants with IGT were randomly assigned to the control (63 cases, 3 lost to follow-up) and treatment groups (64 cases, 4 lost to follow-up) according to the random number table. The control group received lifestyle intervention alone, while the patients in the treatment group took orally 10 g of TYP twice daily in addition to lifestyle intervention for 12 weeks. The rates of patients achieve NGT or experiencing conversion to DM as main outcome measures were observed at 3, 12, and 24 months after TYP treatment. The secondary program measures fasting plasma glucose (FPG), 2-h postprandial plasma glucose (2h PG), glycosylated hemoglobin (Hb A1c), fasting insulin (FINS), 2-h insulin 2hI NS), homeostatic mod el assessment of insulin resistance (HOMA-IR), blood lipid and patients’ complains of Chinese medicine (CM) symptoms before and after treatment. Results: A higher proportion of the treatment group achieved NGT compared with the control group after 3-, 12 - and 24-month follow-up (75.00% vs. 43.33%, 58.33% vs. 35.00%, 46.67% vs. 26.67%, respectively, P <0.05). The IGT to DM conversion rate of the treatment group was significantly lower than that of the control group at the end of 24-month follow-up (16.67% vs. 31.67%, P <0.05). Before treatment, FPG, 2h PG, Hb A1c, FINS, triglyceride (TG), total cholesterol, low- and high-density lipoprotein cholesterol levels had no statistical difference between the two groups (P> 0.05). After treatment, the 2hP G, HbA 1c, HOMA- IR, and TG levels of the treatment groups decreased significantly compared to those of the control group (P <0.05). CM symptoms such as exhaustion, irritability, chest tightness and breathless, spontaneous sweating, cons tipation,and the dark thick and greasy tongue were significantly improved in the treatment group as compared with the control group (P <0.05). No severe reversed events occurred. IGT stage with a disciplined lifestyle delayed IGT developing into type 2 DM .