The most commonly used phrase to prevent and treat diseases is “early diagnosis and early treatment”. However, for each disease, the connotation is different, such as lung cancer. Since the early symptoms of lung cancer are not obvious and typical, it is often in the middle and late stages when symptoms are present, like other diseases, before seeking medical treatment. Therefore, the most effective way is to have regular medical checkups and turn passive into active. At present, the relationship between smoking and lung cancer has been very clear. 1998 retrospective survey of 1 million deaths in China and 250,000 population follow-up survey showed that lung cancer accounted for 15% of smoking-related deaths. Therefore, smokers are a high-risk group for lung cancer, especially those who smoke more than one pack of cigarettes per day and have smoked for more than 30 years. In addition, the incidence of lung cancer in women has increased faster than that of men in recent years, suggesting that air pollution and home renovation may be the culprits of lung cancer. Those with immediate family members suffering from lung cancer, especially those whose parents have lung cancer, should be more alert because lung cancer has a family gathering phenomenon. Patients with a history of tuberculosis should think about the possibility of cancer if there are changes in the lesions on imaging. In Japan, people over 40 years old have lung CT every six months to screen for lung cancer. In China with limited economic conditions, chest X-ray should be taken once a year for general population, and chest X-ray should be taken once every six months for the above-mentioned high-risk group (e.g. smokers over 40 years old), and if economic conditions allow, it is better to do CT plain scan of lung once a year.