Objective To evaluate the antiplatelet efficacy of clopidogrel and ticagrelor in the patients with acute coronary syndrome (ACS) and diabetes mellitus after percutaneous coronary intervention (PCI), and investigate the effect on prognosis by thrombelasto-graphy. Methods A total of 100 patients with ACS and diabetes admitted in our department from June 2016 to January 2017 were prospectively enrolled in this study. They were randomized into clopidolgrel group and ticagrelor group (n=50). Thrombelastography was carried out in 24 to 48 h after PCI for inhibitory effects on arachidonic acid (AA)-induced platelet aggregation, adenosine diphosphate (ADP)-induced platelet aggregation and maximum ADP (MAADP). The incidences of major adverse cardiovascular events (MACE), bleeding events and dyspnea were compared between the 2 groups during the follow-up of 6 months after PCI. SPSS statistics 19.0 was used for data processing. Students’ t test or Chi-square test were adopted for comparison of different data types between groups. Results The patients of ticagrelor group had significantly higher inhibition rates in AA pathway [(72.3±26.6)% vs (54.0±31.4)%, P=0.041] and in ADP pathway [(76.5±22.1)% vs (43.4±28.7)%, P=0.016], but obviously lower MAADP [(33.2±10.5) vs (48.2±13.6)mm, P=0.024] when compared with the clopidogrel group. The patients with AA inhibition rate <50% (14.0% vs 38.0%; P=0.006) and ADP inhibition rate <30% (6.0% vs 28.0%; P=0.003) were notably fewer in the tigcagrelor group than the clopidogrel group. There were no significant differences in the incidences of MACE and dyspnea between the 2 groups. Conclusion Ticagrelor is superior to clopidolgrel in antiplatelet effect in the diabetes patients with ACS after PCI.