Lung cancer occurs in the bronchial mucosa epithelium, also known as bronchial cancer. In recent 50 years, many countries have reported a significant increase in the incidence of lung cancer, which has taken the first place among male cancer patients and is also rapidly increasing in women, taking the second or third place among common malignant tumors in women. The etiology of lung cancer is still not completely clear, but a lot of information shows that long-term heavy smoking is an important causative factor of lung cancer. The incidence of squamous and undifferentiated lung cancer is 4 to 10 times higher than that of nonsmokers who smoke more than 40 cigarettes per day for many years. The incidence of lung cancer in urban residents is higher than in rural areas, which may be related to atmospheric pollution and the presence of carcinogenic substances in cigarette smoke. Therefore non-smoking should be promoted and urban environmental sanitation should be enhanced.