Malnutrition and dyscrasia are very common in cancer patients. Malnutrition is associated with poor treatment tolerance, reduced opportunities for treatment, increased complications, increased morbidity and mortality, prolonged hospital stay, and lower survival rate. Malnutrition not only has an impact on the effect of treatment and quality of life, but also cause huge economic losses and waste of social medical resources. Nutrition therapy as a basic methods of clinical treatment and rehabilitation, has been proved by a large number of evidence-based medicine at home and abroad. The evidence shows that the reasonable and effective nutritional support will not increase the rate of tumor recurrence or metastasis rate and lower survival rate, but can significantly improve the postoperative cancer patients nutrition and immune status, reduce the incidence of complications and postoperative infection, improve the cure rate of patients, reduce the mortality rate, reduce drug and medical expenditure, has a positive for most malnourished cancer patients. In order to apply the medical nutrition therapy on patients with cancer to clinical practice, the consensus based on existing research on the relationship between cancer and nutrition at home and abroad, and combined with the status and characteristics of China's diet. Systematically summarize and analyze the influence of dietary nutritional factors on cancer patients and standardize the principles and steps of oncology nutrition treatment. Apply to clinician, clinical nutrition professionals, nurse, and other health care workers.