Abstract: Objective To investigate the effect of thrombus aspiration(TA) on main adverse cardiac event(MACE) in ST-elevation myocardial infarction(STEMI) patients undergoing primary percutaneous conorary intervention(PCI). Methods Clinical data about 475 STEMI patients admitted to the department of cardiology, Xinjiang Military General Hospital from January 2014 to October 2017 were retrospectively analyzed. By using propensity score matching on gender and age, these patents were divided into two groups, PCI+TA group(n=68) and PCI alone group(n=68). General demographic data, clinical characteristics, coronary artery lesions and PCI parameters of patients in two groups were recorded. The difference of the primary and secondary endpoints and the total MACE occurrence were compared between two groups. Binary logistic regression was used to analyze the main factors influencing the occurrence of MACE. Results The mean number of diseased vessels and the preoperative TIMI flow grade in the PCI+TA group were significantly greater than those in the PCI group alone(P< 0.05, respectively). There was no significant difference in other baseline data between two groups(P> 0.05). The heart rate and blood pressure changes, defibrillation treatment and total MACE during operation in the PCI+TA group were all significantly greater than those in the PCI group(17.6% vs 1.5%; 10.3% vs 0; 20.6% vs 1.5%; all P< 0.05). Incidences of ventricular arrhythmia and death in the PCI+TA group were higher than those in the PCI(4.4% vs 1.5%; 2.9% vs 0%), but the differences were not significant(P> 0.05). TIMI2 flow was observed in all patients immediately after PCI. Binary logistic regression analysis showed that TA(OR, 18.531; 95% CI, 2.262 to 151.800) was the main factor affecting the occurrence of MACE. Conclusion There is no difference in the improvement of immediate TIMI flow grade by using TA before PCI between two groups, but TA may increase the risk of MACE occurrence and should be selected carefully in clinical practice.