Objective: To explore the application effect of western medicine and Dachaihu decoction in obese patients with type 2 diabetes, and the influence on insulin resistance.Methods: Eighty-eight patients with obese type 2 diabetes admitted to our hospital from January 2023 to January 2025 were selected to participate in the study. They were randomly divided into two groups by computer. The control group was treated with western medicine, and the study group was treated with combination therapy (western medicine and Dachaihutang), with 44 cases in each group. The therapeutic effects of the two groups were analyzed.Results: The therapeutic effect of the study group was higher (P < 0.05). The symptom score of the study group was low (P < 0.05). The blood sugar level in the study group was low (P < 0.05). The islet function in the study group was better (P < 0.05).Conclusion: Western medicine combined with Dachaihu decoction can improve the blood sugar level and islet function of obese type 2 diabetic patients, alleviate the influence of patients" symptoms, and ensure patients" health, which is worth popularizing.