Avoidance of food for tumor patients is a very important yet complex issue that almost all patients and their family members may ask about. Since the patient’s diet can directly affect the development of the disease and treatment effect, tumor patients should pay attention to the dietary taboos and try to avoid foods that can promote the progress of the disease or are unfavorable to the treatment. Chinese medicine advocates the avoidance of food, which is recorded in many classical works of Chinese medicine. Depending on the patient’s constitution, the nature of the disease, the treatment method and the drugs used, the type and scope of the taboo may vary. By avoiding the mouth, we can prevent the development of disease from the aspect of diet and reduce or eliminate the adverse effects on certain treatment. First of all, spicy, cold, greasy and indigestible foods should be avoided for tumor patients. Some foods that can aggravate the disease or induce disease attack are called “hairy foods”, such as scallop, dog meat and chili pepper. However, these foods are not “hairy” for all diseases, and their effects can vary from person to person and from disease to disease. Some are related to allergic diseases, such as asthma. Some are related to soreness and toxicity. For tumor patients, there is no definite conclusion in modern medicine whether the above “hair products” can play a role. Secondly, depending on the patient’s constitution and the nature of the disease, the nature and taste of the food should be considered whether to avoid the mouth. Any food that is unfavorable to the patient should be avoided. If the disease is Yin or cold, cold products such as cold melons and fruits, greasy things should be avoided. If the disease is Yin deficiency, often with deficiency heat, should avoid hot and spicy products, such as chili, cinnamon, dog meat, etc. In conclusion, there are few universal food taboos for tumor patients, except for tobacco, alcohol, greasy and stimulating foods. Often, according to the dialectic of Chinese medicine, there are different taboos for different people, different diseases and different treatments. We cannot generalize and mechanically prescribe what patients can or cannot eat. Although we should respect the practice of our predecessors and some traditional taboos, we should oppose the practice that is so demanding that patients are at a loss as to what to eat. The patient’s nutritional status eventually deteriorates, affecting treatment and recovery. Depending on the strength of the patient’s condition and the digestive and absorption functions of the spleen and stomach, necessary dietary supplements or dietary therapy should be given to compensate for the excessive consumption of tumor and improve the immune function and anti-cancer ability of the body.