Abstract： Objective： To observe the curative effect of Didang Decoction combined with Metformin Hydrochloride Sustained- Release Tablets for type 2 diabetes mellitus (T2DM)，and its effect on intestinal microecology and glucose and lipid metabolism. Methods：A total of 60 patients with T2DM were selected as the research objects and divided into the control group and the observation group according to the random number table method，with 30 cases in each group. The control group was treated with Metformin Hydrochloride Sustained- Release Tablets，and the observation group was treated with Didang Decoction on the treatment of the control group. Both groups were treated for 8 weeks. The clinical effects were compared between the two groups. The changes in traditional Chinese medicine (TCM) syndrome scores， glucose and lipid metabolism indicators [fasting blood glucose (FBG)， 2- hour postprandial blood glucose (P2hBG)， triglycerides (TG)， total cholesterol (TC)， high- density lipoprotein cholesterol (HDL- C)， and fasting insulin]，oxidative stress indicators [superoxide dismutase (SOD)，reactive oxygen species (ROS)， and malondialdehyde (MDA)]， and intestinal microecology indicators were compared in the two groups before and after treatment. Results：The total effective rate of clinical effect was 93.33% in the observation group，and 73.33% in the control group，the difference being significant (P＜0.05). After treatment，the TCM syndrome scores of fatigue， irritability， bitter mouth and dry throat， and red tongue and yellow coating in the two groups were decreased when compared with those before treatment (P＜0.05). The TCM syndrome scores in the observation group were lower than those in the control group (P＜0.05). After treatment，the levels of FBG，P2hBG，HOMA-IR，and TG in serum in the two groups were decreased when compared with those before treatment (P＜0.05)，and the levels of HDL-C in serum were increased when compared with those before treatment (P＜0.05)；the levels of FBG，P2hBG，HOMA-IR，and TG in serum in the observation group were lower than those in the control group (P＜0.05)，and the HDL-C level in serum was higher than that in the control group (P＜0.05). There was no significant difference being found in the comparison of TC before and after treatment between the two groups (P＞0.05). After treatment，the SOD levels in serum in the two groups were increased when compared with those before treatment (P＜ 0.05)，and the ROS and MDA levels in serum were decreased when compared with those before treatment (P＜0.05)；the SOD level in serum in the observation group was higher than that in the control group (P＜ 0.05)，and the ROS and MDA levels in serum were lower than those in the control group (P＜0.05). After treatment，the colony numbers of bacteroides，bifidobacterium，clostridium leptum，and lactobacillus in the two groups were increased when compared with those before treatment (P＜0.05)， and the colony numbers of enterococcus and enterobacterium were decreased when compared with those before treatment (P＜0.05)； the colony numbers of bacteroides， bifidobacterium， clostridium leptum， and lactobacillus in the observation group were higher than those in the control group (P＜0.05)，and the colony numbers of enterococcus and enterobacterium were lower than those in the control group (P＜0.05). Conclusion： Didang Decoction combined with Metformin Hydrochloride Sustained- Release Tablets can effectively alleviate the clinical symptoms of patients with T2DM， improve glucose and lipid metabolism and intestinal microecology，and reduce the oxidative stress reactions of the body.