OBJECTIVE： To discuss clinical efficacy and safety for the shifting from clopidogrel to ticagrelor in acute coronary syndrome （ACS） patients. METHODS： In retrospective study， clinical data of ACS inpatients receiving clopidogrel initially and ticagrelor instead were collected from our hospital during Jan. 2013 to Jun. 2014. They were divided into low response group and response group by inhibition rate of ADP activator. The rehospitalization rate of recurrent cardiovascular events， ticagrelor-related ADR as respiratory depression and bleeding were compared between 2 groups after followed up 1， 3， 6 and 9 months. RESULTS： 124 patients were included， among which there 34 patients in low response group and 90 patients in response group. The proportion of smokers in response group was higher than in low-response group， and the proportion of patients with hypertension in low response group was higher in response group， with statistical significance （P＜0.05）. After using ticagrelor instead for 1， 3， 6 and 9 months， the rehospitalization rates resulting from recurrent cardiovascular events were 6.5％， 7.2％， 8.1％ and 10.5％， respectively. There was no statistical significance in rehospitalization rates resulting from recurrent cardiovascular events between 2 groups （P＞0.05）. In follow-up， 12 patients suffered from dyspnea and 3 suffered from gingival bleeding. CONCLUSIONS： Ticagrelor can improve the low platelet response of clopidogrel that could reduce the rehospitalization rates resulting from recurrent cardiovascular events. But should be carefull of the risk of dyspnea and rehaemorrhagia induced by ticagrelor.