Objective:To study influence of insulin on myocardial microcirculation of patients with coronary heart disease (CHD)complicated type 2 diabetes mellitus (T2DM)after percutaneous coronary intervention (PCI).Meth-ods:A total of 65 patients,who was confirmed as CHD by coronary angiography and fractional flow reserve (FFR)<0.75 measured by pressure guidewire,were enrolled.After drug-eluting stent implantation,index of microcircula-tion resistance (IMR)was measured.According to insulin usage or not,they were divided into insulin therapy group (insulin group,n=30)and pure oral hypoglycemic agent therapy group (pure hypoglycemic agent group,n=35). After six-month follow up,IMR was reviewed,and IMR was compared between two groups.Results:There was no significant difference in incidence rate of major adverse cardiovascular events (MACEs)between two groups,P =0.07. On six months after PCI,IMR in insulin group was significantly lower than that of pure hypoglycemic agent group [(24.5±3.1)U vs.(30.2±4.3)U,P <0.05].Conclusion:Insulin therapy can improve myocardial micro-circulation in patients with coronary heart disease complicated type 2 diabetes mellitus after PCI.