ObjectiveTo investigate the no reflow risk factors after percutaneous coronary intervention in ST elevation myocardial infarction patients.MethodSample size, mean ± standard deviation (SD) or frequencies (percent) of normal and no reflow groups were extracted from each study.ResultsOf 27 retrospective and prospective studies, we found that increasing risks of no reflow were associated with advanced age, male, family history of coronary artery disease, smoking, diabetes mellitus, hypertension, delayed reperfusion, killip class ≥2, elevated blood glucose, increased creatinine, elevated creatine kinase (CK), higher heart rate, decreased left ventricular ejection fraction (LVEF), collateral flow ≤1, longer lesion length, multivessel disease, reference luminal diameter, initial thrombolysis in myocardial infarction (TIMI) flow, and high thrombus burden. Moreover, initial TIMI flow ≤1 and high thrombus burden had the greater impact on no reflow (OR95%CI = 3.83 [2.77–5.29], p < 0.0001 and 3.69 [2.39–5.68], p < 0.0001, respectively).ConclusionOur meta-analysis reveals that initial TIMI flow ≤1 and high thrombus burden are the most impacted no reflow risk factors.