According to the World Health Organization, one third of tumors in the world can be prevented, one third of tumors can be detected early and cured, and the other third can reduce the pain and prolong the survival period. Although the treatment of tumors in the world has made considerable progress in recent years, such as endocrine therapy for breast cancer, radiotherapy, interventional and targeted therapy for many kinds of tumors combined with surgery and Chinese medicine have greatly improved their efficacy and even cure rate, tumors are still a world medical problem. The prevention of tumors, early detection of tumors and the best time for treatment are still the most important issues in the field of tumor prevention and treatment. The focus of tumor prevention and treatment is to closely observe some precancerous lesions and certain high-risk groups of tumors (with family history of related tumors, chronic diseases, unreasonable lifestyle and reaching a certain age, generally above 35 years old), so that precancerous lesions can be transformed or the occurrence of tumors can be detected at an early stage for favorable treatment timing. For example, severe hyperplasia of esophagus is a precancerous lesion of esophageal cancer, hepatitis with active viral replication (mostly hepatitis B) is a risk factor for liver cancer, atypical hyperplasia of stomach, chronic atrophic gastritis and gastric ulcer are precancerous lesions of gastric cancer, a few (3-5%) of breast hyperplasia can develop into breast cancer, a few (5%) of gallbladder polyps can develop into malignant tumor of gallbladder, and so on. In summary, all chronic diseases that cause continuous tissue destruction and tissue regeneration are prone to develop new cell mutations and tumors. The corresponding measures are active treatment of precancerous lesions, regular observation, and surgery if necessary. Lifestyle-related tumors: smokers or passive smokers are prone to lung cancer, women who drink more milk are more likely to develop breast cancer (due to high estrogen levels), those who eat more fine foods have a higher incidence of colon cancer, and those who eat more coarse foods and irregular diet are prone to develop stomach cancer. A balanced diet, fresh vegetables, fruits and mushrooms can enhance the immunity of the body and prevent the occurrence of tumors.