The use of diet to prevent and treat diseases has a long history in China. Diet therapy is more significant for tumor patients, which is not only helpful to relieve clinical symptoms of cancer patients, but also beneficial to their recovery. When cancer patients use diet therapy, they should grasp the following three basic principles. I. Emphasize balanced nutrition and focus on supporting and replenishing deficiency Cancer patients’ “internal deficiency” is the main contradiction in the process of disease occurrence and development. Cancer is caused by deficiency, cancer is caused by deficiency, and deficiency is the basis of deficiency. The purpose of food therapy is to ensure cancer patients have enough nutrition, improve the body’s ability to resist disease and promote their recovery, and the general principle should be to support and supplement deficiency. Food therapy for cancer patients should be nutritious, diversified and balanced. It is not beneficial if it is not biased. Like other diseases, cancer patients have different yin and yang, cold and heat, deficiency and reality. Food is also different from hot, cold, warm and cool, pungent, sweet, bitter, sour and salty. The five tastes of food should be cold for heat and warm for cold; each of them has its own place in the mouth: sweet to the spleen, pungent to the lung, salty to the kidney, bitter to the heart and sour to the liver. Clinically, food therapy must be in line with the principles of diagnosis and treatment, and should be different from disease to disease and from person to person, not uniform. For example, if the evidence is toxic-heat congestion, the evidence of internal incandescence, the patient’s symptoms of heat, you can not invest in warm food tonic, such as cinnamon, litchi, venison, ginseng, mutton, dog meat, prawns, etc., but should be given to have the effect of detoxification of heat vegetables, food, such as fishy grass, horsetail, capers, duck, rutabaga, asparagus, etc.. If the patient has a weak spleen and stomach after surgery and has little food, bloating and loose stools, the patient should be given foods that strengthen the spleen and stomach, such as yam, poria, lotus seeds, hen’s nest, malt, etc. For example, during or after radiotherapy, due to heat toxin injury to yin, the symptoms include dry mouth, dry throat, light tongue coating and thin pulse, so the patient should eat more sweet and cold foods to nourish yin and produce fluid, such as water chestnut juice, water chestnut juice and pear juice, and avoid stimulants such as aromatic dryness, braising, spicy, tobacco and alcohol. Patients with lung cancer who have cough, coughing phlegm or blood in phlegm are suffering from Yin deficiency and phlegm-heat, so they should avoid spicy, fishy and fishy hairy products that rob Yin and produce phlegm, as well as food with congestion; when various malignant tumors in liver, stomach and abdominal cavity are complicated with abdominal distension and ascites, it is appropriate to eat more light permeable diuretic food and avoid food with congestion, such as taro, sweet potato, onion and pumpkin. In short, we should pay attention to food identification and reasonable food therapy. 3.Selecting anti-cancer foods, strive for targeted medicine and food, some foods have both therapeutic and anti-cancer effects, so they can be selected and applied in a targeted way. Foods beneficial to digestive tumors include leek, Ulva, cabbage, Chinese cabbage, lily, cuttle beans, etc. Among them, cuttle beans are sweet and warm. Among them, knife bean is sweet and warm in nature, which has the function of warming the middle and lowering the qi, tonifying the kidney and strengthening the spleen, and is used in folklore with clove and persimmon to treat esophageal cancer, stomach cancer and liver cancer. Foods in daily life, such as garlic, soy products and green tea, are also good anti-cancer medicines. Some recent studies have shown that many foods are beneficial in the prevention and treatment of cancer. For example, goose blood can improve symptoms and raise white blood cells for malignant tumors of lung, stomach, lymph and nasopharynx, which has been developed into tablets; coix seeds contain coix seed fat, which has obvious inhibitory effect on cancer cells and is commonly used clinically for lung cancer, intestinal cancer, cervical cancer and choriocapillaris epithelial cancer; mung beans with licorice and chemotherapy drugs have the effect of cooling and detoxifying and reducing side effects; kombu, seaweed and nori treat thyroid, neck tumors and The mushroom, Ulva lactuca and cinnamon have different degrees of immunity and therapeutic effects; white lentil can improve the transformation rate of lymphocytes in patients with nasopharyngeal cancer; sea cucumber polysaccharide extracted from ginseng can inhibit DNA of breast cancer cells and protect liver function. In addition, there are still more varieties such as fig, ground ear, almond, water chestnut, plum, lily, silver fungus, yellow essence, mussel, snail, bird’s nest, etc., all have anti-cancer effects.