Aim To compare effectiveness of atorvastatin to atorvastatin co-administration ezetimibe on modifying total cholesterol （TC）, low density lipoprotein cholesterol （LDLC）, endothelin-1 （ET-1） and nitric oxide （NO） and protecting vascular endothelial function and the security in patients with acute coronary syndrome （ACS）. Methods 125 patients with ACS consecutively enrolled from June 2011 to December 2011 were divided randomly into atorvastatin group （20 mg qn） and co-administration group （atorvastatin 20 mg qn＋ezetimibe 10 mg qn） TC, LDLC, ET-1 and NO were measured at admission and 12 weeks after treatment. Results （1）TC, LDLC, ET-1 levels were lower and NO higher significantly in two groups than pre-treatment, however, TC, LDLC, ET-1 levels were more lower and NO more higher 12 weeks later in co-administration group than atorvastatin group （TC: 3.20±0.55 mmol/L vs 4.28±0.59 mmol/L, P<0.01 LDLC: 1.92±0.33 mmol/L vs 2.63±0.53 mmol/L, P<0.01 ET-1: 3.88±1.15 ng/L vs 4.49±0.85 ng/L,P<0.05 NO: 80.39±7.87 μmol/L vs 72.18±12.16 μmol/L, P<0.05）, the lower TC, LDLC, ET-1 levels were 17.5%, 17.4% and 10.4%, respectively, the higher NO level was 14.2%. （2）If LDLC＜2.60 mmol/L was regard as target value, target rate in atorvastatin group was 47.6% and in co-administration group was 81.8%. （3）Few adverse events in two groups occurred and no statistical differences were found between them. Conclusion Atorvastatin combining ezetimibe in ACS patients will bring better effectiveness on modifying lipid and protecting vascular endothelial function and good security.