Abstract: Objective To investigate the value of red distribution width (RDW) in predicting the prognosis of STEMI patients undergoing primary PCI． Methods A total of 520 patients with diagnosis of STEMI who underwent emergency primary PCI from December 2013 to February 2016 in the department of cardiology, Navy General Hospital were included in this retrospective study．According to the preoperative RDW, STEMI patients were divided into low RDW group (RDW≤13%, n=389) and high RDW group (RDW> 13%, n=131) with a median split (median 13%)． The predictive value of preoperative RDW level and the incidence of MACE events were compared between two groups during hospitalization and one-year after PCI, and the prognostic factors of STEMI patients after PCI operation were investigated by univariate and multivariate Logistic regression analysis． Results Compared with the low level of RDW group, the incidences of MACE events in the high RDW group after PCI during the postoperative hospitalization (4．7% vs 15．3%, P< 0．001), and 1 year after PCI (9．3% vs 29%, P< 0．001) were higher． Univariate Logistic regression analysis found that age (OR=1．019, 95%CI: 1．001-1．039, P=0．044), Hb (OR=0．985, 95%CI: 0．972-0．998, P=0．024), RDW (OR=2．212, 95%CI: 1．602-3．045, P< 0．001) were related with the occurrence of MACE events． Multivariate Logistic regression analysis showed that only RDW (OR=1．831, 95%CI: 1．372-2．445, P< 0．001) was independent risk factor． Conclusion Reoperative RDW level can predict the prognosis of patients with STEMI undergoing emergency PCI, and patients with high RDW level is more likely to develop of MACE．