Although the incidence of gastrointestinal hemorrhage after cardiac surgery is low, the mortality rate is high. Early detection and diagnosis of gastrointestinal hemorrhage are difficult. The high risk phases including preoperation, intraoperation and postoperation. Preoperative high risk comorbidities include gastrointestinal ulcer, hypertension, coronary heart disease and chronic renal failure. Intraoperative high risk factors include decreased gastrointestinal blood perfusion due to cardiopulmonary bypass, inflammatory factors releasing, coagulation disorders, and thrombosis. Postoperative high risk factors include hypotension, low cardiac output, prolonged mechanical ventilation, etc. This article retrospectively summarized high-risk factors and pathogenesis of gastrointestinal hemorrhage after cardiac surgery, in order to improve prevention and treatment of gastrointestinal hemorrhage.