Early enteral nutrition after cardiopulmonary bypass (CPB) has been shown to have beneficial effects on intestinal integrity, lower mortality and also on the patient’s immunocompetence. Even in critical patients after CPB, enteral nutrition should be reasonable to start early and also be supplemented by parenteral nutrition in order to meet energy requirement. We conclude that enteral nutrition is preferable in the majority of patients with severe hemodynamic failure, but gastrointestinal complication and hypocaloric feeding should be simultaneously noticed. This paper comprehensively described enteral nutrition’s protective mechanism and effects on digestive system, enteral nutrition’s implementing methods after CPB, and problems or prospects needing attention in execution.