According to statistics, nearly 80% of lung cancer patients are already at an advanced stage when they are discovered. Late diagnosis is one of the important reasons for the low overall survival rate of lung cancer patients. Therefore, if the risk factors of lung cancer are known, people can target their prevention, or at least do regular medical checkups and close observation to nip lung cancer in the bud. The risk factors of lung cancer can be roughly arranged in the following order. Therefore, five categories of people should be alert to lung cancer invasion. Those with family history of tumor. Many tumors have obvious family gathering characteristics, including lung cancer, colon cancer, breast cancer, etc. In a study done in Japan, researchers divided patients with lung cancer in their immediate family and those without a family history of lung cancer into two groups, and the former were twice as likely to develop the disease as the latter. The heritability of lung cancer is more pronounced in women. Clinical experience shows that people with a family history of other tumors also have a higher risk of developing lung cancer than those without a family history of tumors. People with a history of tuberculosis. Tuberculosis is a chronic infectious disease that occurs in young people, with 80% of tuberculosis occurring in the lungs. TB was once a major killer of humans, claiming hundreds of millions of lives. Clinical experience has shown that many old TB lesions can later become the cradle of lung cancer. Some patients who had tuberculosis in their early years were later found to have progressively larger nodules, which were eventually pathologically diagnosed as scar carcinoma. China is one of the 22 countries in the world with a high burden of tuberculosis, with more than 400 million people infected. This large population of TB infected people may have a causal relationship with the high incidence of lung cancer in China in recent years. Smokers and passive smokers. Epidemiological and scientific experiments have successively proved that cigarettes contain 42 carcinogenic substances and that the development of lung cancer is closely related to smoking. Studies have shown that the prevalence of lung cancer among long-term smokers is 10-20 times higher than among nonsmokers. In addition, among non-smokers who develop lung cancer, 25% are passive smokers. The harmful substances inhaled by passive smoking are often more powerful than those inhaled by active smoking. The younger the smoker, the more they smoke, and the longer they smoke, the more dangerous they are; women smokers have twice the risk of developing lung cancer as men. Those who are exposed to harmful chemicals. In recent years, air pollution is becoming more and more serious, and people are more and more in “close contact” with harmful chemicals, and lung cancer is also highly prevalent. People with high mental stress. People who are overly stressed or suffer from mental trauma are often in a state of stress for a period of time, and at this time, the immune function of human body is low, so the disease will take advantage of the situation. To sum up, prevention of lung cancer should follow five principles: people with family history of tumor should maintain a healthy lifestyle and have annual chest X-ray or lung CT; people with history of tuberculosis should actively treat tuberculosis and have regular medical checkups; smokers must quit smoking and non-smokers should stay away from second-hand smoke and third-hand smoke; avoid long-term exposure to harmful chemicals and use protective gear if necessary; maintain a good mind, positive and optimistic To cope with all kinds of unpredictability in life and work.