Lung cancer has the highest incidence and mortality rate among all kinds of malignant tumors and is a serious threat to people’s health. How to prevent lung cancer has become a topic of concern. First of all, smoking is considered to be the most important causative factor of lung cancer. Smoking includes active smoking and passive smoking. Smokers who smoke are active smokers. Non-smokers who inhale smoke exhaled by smokers for more than 15 minutes/day at least one day a week are passive smokers. The International Health Organization has published that if a person has a smoking index greater than 400 (number of cigarettes smoked per day x years of smoking), he or she is defined as being at high risk for lung cancer. In recent years, it has also been found that “third-hand smoke” can also be harmful to human health, especially to the health of infants and children. “Third-hand smoke” means that no matter where you smoke, the harmful particles in the smoke will be adsorbed on your hair, skin, clothes, carpets, sofas and car seat covers, and even if you smoke and then come into contact with your child, your child will still be exposed to the harmful substances produced by burning cigarettes in the environment. This requires people to understand the dangers of smoking and to take the initiative to quit for the health of themselves and their families, especially doctors should set a good example. In addition, it is more important for the whole society to take action and increase the efforts to control tobacco. The second is air pollution, including indoor air pollution and outdoor air pollution. Studies have found that formaldehyde and radon gas released from indoor decoration materials may be risk factors for the occurrence of lung cancer. Therefore, renovation should use environmentally friendly materials as much as possible and ventilate for a period of time after renovation before moving in. In addition, the high temperature fumes that women are exposed to when cooking for a long time can also increase the risk of lung cancer. Therefore, it is important to pay attention to clean and ventilated kitchen when cooking and reduce high temperature frying. Outdoor air pollution: industrial exhaust and automobile exhaust contain carcinogenic substances, especially benzo(a)pyrene, which has the most obvious carcinogenic effect. With the emission of pollutants, hazy weather is becoming more and more frequent. The fine particles suspended in the air are easily absorbed by the human body and may adhere directly to the respiratory tract and lung lobes, causing rhinitis, bronchitis and other diseases, and long-term exposure can induce lung cancer. Therefore, the country should pay attention to environmental protection and control environmental pollution. People should pay attention to wearing masks when going out on hazy days, and avoid going out on heavy hazy days as much as possible. Thirdly, frequent exposure to asbestos, arsenic, uranium, nickel and chromium are also risk factors for lung cancer, such as the tin mine in Jielao, Yunnan Province, which is a high incidence area for lung cancer. Therefore, it is important to avoid frequent exposure to these substances. In addition, some chronic lung diseases such as chronic bronchitis, tuberculosis and diffuse interstitial lung fibrosis have a higher risk of developing lung cancer than other people. Therefore, it is important to pay attention to the diagnosis and treatment of chronic lung diseases.