For critically ill patients, enteral nutrition at early phase can not only provide nutrition but also maintain the function and microecology of intestine. The therapeutic effects of medicines depend on their dosages, and so does nutrition therapy. Ideally, the quantity and quality of enteral nutrition make maximum benefit and minimum damage in critically ill patients, with the ultimate goal of sufficient nutrition therapy and no iatrogenic malnutrition. Intolerance of early enteral nutrition is a common problem, and challenge for critically ill patients. Improper nutrition therapy will have adverse and even harmful effects, which should be well learned by doctors and nurses of intensive care unit. In serious or some special medical situations, regimen of nutrition should be evaluated and adjusted timely to achieve the ideal goal and make maximumbenefit for patients.