Aim To investigate the effects of 10-23DNA enzyme(ED5) on endothelial function and ultrastructure change of Carotid Artery after injured artery in rats. Methods Ninety-six rats were randomly divided into sham-group,control-group 1,control-group 2 and ED5-group(n=24).The models of endothelial denudation of rats were made by using balloon catheter,FITC-ED5 was delivered to the artery wall of ED5-group in a total of 200 μL solution.Rats of control-group1 were given 200 μL 1 mmol/L MgCl2.Rats of control-group2 were given FuGENE6 Reagent.Six rats were killed at the 3rd,7th,14th,21th day after balloon injury.The serum level of nitric oxide and nitric oxide synthase and endothelin were detected.At the same time,to observe pathological change of injured arteries by optical microscope and electron microscope. Results The serum level of nitric oxide and nitric oxide synthase in ED5-group were higher than those in 2 control groups,increased significantly on the 14th day(nitric oxide: 57.1±1.9 μmol/L vs 38.7±1.9 μmol/L and 57.1±1.9 μmol/L vs 38.3±1.9 μmol/L,p<0.05;nitric oxide synthase: 11.1±0.4 μmol/L vs 8.1±0.4 μmol/L and 11.1±0.4 μmol/L vs 8.0±0.4 μmol/L,p<0.05);but endothelin in ED5-group was lower than that in 2 control groups,obviously different on the 14th day(111.2±7.2 pg/L vs 136.6±7.2 pg/L and 111.2±7.2 pg/L vs 135.5±7.2 pg/L,p<0.05).Compared with ED5-group,the neointimal thickness in 2 control groups increased significantly on the 21th day after balloon injury(64.0±4.2 μm vs 81.1±4.9 μm and 64.0±4.2 μm vs 79.5±3.9 μm, p<0.01).The vascular smooth muscle cell of neointima in 2 control groups may be contractile type,but vascular smooth muscle cell of neointima in ED5-group may be synthetic type. Conclusion The ED5 can improve the endothelial function after artery injury and inhibit the phenotype transform of vascular smooth muscle cells,and reduce the degree of neointimal hyperplasia.