Objective: To evaluate the effectiveness and safety of Taizhian (泰脂安, TZA) capsule combined with Simvastatin (Sim) in treating hyperlipidemia in diabetes mellitus (DM) patients. Methods:Eighty cases of type 2 DM patients with hyperlipidemia were randomized into two groups, 40 in each group.The patients in the treated group took orally TZA capsules at the dose of 0.9 g 3 times a day and Sim 10 mg at bedtime. And the patients in the control group were treated with Sim 20 mg alone at bedtime. Both regimens lasted for 12 weeks. Before and after the study the changes of blood lipid levels and adverse reaction were investigated. Results: The serum levels of total cholesterol (TC), triglycerides (TG) and low density lipoprotein-cholesterol (LDL-C) were decreased respectively by 28.8%, 18.2% and 26.3% in the treated group; and by 29.4%, 19.4% and 24.6% in the control group. On the contrary, high density lipoprotein-cholesterol (HDL-C) was increased by 23.5% in the treated group and by 29.4% in the control group. All these changes were statistically significant before and after treatment (all P＜0.05), but they did not differ statistically between the two groups (P＞0.05). There was no significant changes in hemoglobin A1 c (HbA1C). Patients in the treated group did not develop any adverse reactions. However, ALT was found to be higher above the normal range in 5% of the patients in the control group. Conclusion: In treating hyperlipidemia in DM patients, combination of TZA with Sim 10 mg taken daily achieved satisfactory efficacy which was similar to Sim 20 mg daily alone. But the combination therapy conducted in the treated group proved to be better in safety, and could overcome adverse reactions resulting from Sim that was seen in the control group.