Objective To investigate the incidence and risk factors of massive gastrointestinal hemorrhage (MGH) in the patients with coronary artery diseases treated with elective percutaneous coronary intervention (PCI). Methods Consecutive 4239 patients with non-ST elevation acute coronary syndrome successfully treated with elective PCI in Anzhen Hospital from January 2012 to December 2014 were enrolled in this study. According to the occurrence of MGH or not within 1 year after PCI, the subjects were divided into MGH group (n=47) and non-MGH group (n=4192). The clinical data, MGH events and mortality in 1 year of follow-up were compared between the 2 groups. Results The incidence of MGH was 1.11% (47/4239) in the subjects. The proportion of the patients with preoperative administration of warfarin and low-molecular-weight heparin was significantly higher in the MGH group than in the non-MGH group (P<005). Multivariate logistic regression analysis revealed that advanced age (>75 years, OR=125, P=0031), anemia (OR=118, P=0037), history of gastrointestinal hemorrhage (OR=149, P=0005) and chronic renal insufficiency (OR=227, P=0001) were independent predictors for MGH in the patients undergoing elective PCI. In 1 year’s follow-up, the mortality was obviously higher in the MGH group than in the non-MGH group (64% vs 32%, P<0001). Conclusion Clinicians should adjust the type and dosage of antiplatelet drugs based on the patient’s age, body mass and renal function, and correct anemia and protect renal function to decrease the occurrence of MGH.