Objective: To investigate the relationship between Helicobacter pylori (Hp) infection and the prognosis of acute coronary syndrome (ACS) in a Chinese population and to explore the significance of Hp eradication therapy in preventing major adverse cardiac events (MACE) and upper gastrointestinal bleeding (UGIB) in patients on dual antiplatelet treatment. Methods: To analyze 472 ACS patients with drug-eluting stent (DES) implantation from January 1, 2008 to December 31, 2010 in the department of cardiology at Beijing Mentougou District Hospital. Patients were divided into three groups: Group 1, the Hp-negative patients (Hp-); Group 2, the Hp-positive patients with eradication therapy (Hp+ Therapy); and Group 3, the Hp-positive patients without eradication therapy (Hp+ No Therapy). All patients took 13C urea breath test, high sensitive C-reactive protein (hs-CRP)，homocysteine (HCY) and other biochemical indicators. The investigators explored the correlations of Hp eradication therapy with MACE (including recurrent myocardial infarction, revascularization and death) and UGIB after 3 to 5 years of follow-up using survival analysis.