Lung cancer occurred in bronchial epithelium, also known as bronchial cancer. The past 50 years many countries have reported the incidence of lung cancer increased significantly in the male lung cancer patients have been on top of the list. The etiology of lung cancer has not yet entirely clear, large amounts of data indicate that a large number of long-term cigarette smoking is lung cancer as an important pathogenic factors. Years of smoking 40 cigarettes a day or more, and undifferentiated squamous cell lung cancer than non-smokers high rate 4 ~ 10 times the incidence of lung cancer for urban residents than rural high, which may be related to atmospheric pollution and dust contained in letter cancer substances. So do not smoke should be promoted and strengthened the work of urban environmental sanitation.