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 the 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 The “internal deficiency” of cancer patients 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 sufficient 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 consistent with the principle of diagnosis and treatment, depending on the disease, different 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, reed, 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. If lung cancer patients have cough, coughing phlegm or blood in phlegm, they should avoid spicy, fishy and fetid food that can rob yin and produce phlegm, as well as congestion food; if various malignant tumors in liver, stomach and abdominal cavity are complicated with abdominal distension and ascites, they should eat more light permeable diuretic food and avoid congestion food such as taro, sweet potato, onion and pumpkin. In short, we should pay attention to food identification and reasonable food therapy. 3.Select anti-cancer foods, and strive to have 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 in nature. 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 by the folk to treat esophageal cancer, stomach cancer and liver cancer with cloves and persimmon. Foods in daily life, such as garlic, soy products and green tea, are also good anti-cancer agents. 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 seed contains coix seed fat, which has obvious inhibitory effect on cancer cells and is commonly used clinically for lung cancer, intestinal cancer, cervical cancer and chorioepithelial cancer; mung bean with licorice is used with chemotherapy drugs, which has 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 the ginseng can inhibit the 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 effect.