Clopidogrel, in addition to aspirin, is the cornerstone of therapy in patients suffering from Acute coronary syndrome. However, the platelet inhibitory response to clopidogrel varies substantially among individuals. Several loss‐of‐function polymorphisms have been identified that may influence clinical outcome in patients presenting with acute coronary syndromes (ACS) who are treated with clopidogrel. However their contribution to high on-treatment platelet reactivity (HPR) in clopidogrel treated Chinese patients is less known. As far as we know, ticagrelor is not dependent on gene-based metabolic activation and demonstrated greater clinical efficacy than clopidogrel in a recent secondary prevention trial. we will conduct an interventional study to compare the antiplatelet efficiency between clopidogrel and ticagrelor by the guidance of CYP450 2C19*2 (CYP2C19*2) , using Taqman genotyping method.