Objective To evaluate the clinical efficacy and safety of dipeptide base peptidase 4 ( DPP-4 ) inhibitors alone or combined with metformin in curing type 2 diabetes mellitus (T2DM).Methods 90 patients diagnosed with type 2 diabetes in Tangshan Fengrun District Hospital and Tangshan Checheng Hospital were selected and randomly divided into therapy group ( DPP4 inhibitor ) , control group ( metformin ) and combination therapy group with 30 cases in each group.And treatment for three months, the free blood glucose (FPG), 2-hour postprandial blood glucose (2hPG), glycated hemoglobin (HbA1c) levels and other indicators were compare before and after treatment, and the rates of hypoglycaemia and adverse events during treatment were monitored and counted.Results After 3 months of treatment, the free blood glucose, 2-hour postprandial blood glucose, LDL-C and HbA1c levels were significantly decreased, the difference was statistically significant (P<0.05) while the combination therapy group compared with the the therapy group and control group with better results.The incidence of side-effect in the combination therapy group is significantly lower than the therapy group and control group, the difference was statistically significant (P<0.05).It is no cases of hypoglycemia occurs in the combination therapy group, and had a smaller effect on BMI.Conclusion DPP-4 inhibitors combined with metformin in patients with type 2 diabetes has better efficacy and safety.