Many people wish to know how to prevent lung cancer. According to the statistical analysis on the incidence of lung cancer jointly conducted by the Health Statistics Information Center of the Ministry of Health and the National Office of Cancer Control and Research, the main risk factors for lung cancer are found to be smoking, low intake of fresh vegetables, history of respiratory diseases, low body mass index, psychological factors, kitchen fumes, air pollution, etc. In the eight cities surveyed, such as Beijing and Shanghai, about 90% of the incidence of lung cancer can be explained by these factors. 1.Smoking Smoking is defined as smoking more than 1 cigarette per day for more than 6 months. In the study, it was found that men who smoked more than 2 boxes per day had 20.4 times the risk of lung cancer than normal. The higher the amount of cigarettes smoked and the longer the duration of smoking, the greater the risk. The risk for passive smokers was associated with the number of years of passive smoking. 2.Low intake of fresh vegetables In daily life, the intake of more vegetables and moderate amount of fresh fruits has a protective effect on lung cancer in men; the greater the intake, the more obvious the protective effect. The intake of more vegetables has a protective trend for women, although it is not as obvious as that for men. In addition, sour (vinegar) foods, spicy foods, onion and garlic foods have protective effects on lung cancer, while fried foods and pickled foods increase the risk of developing the disease. 3.History of respiratory diseases History of previous lung diseases (asthma, chronic obstructive pulmonary emphysema, pneumonia and tuberculosis) is a risk factor for lung cancer, among which tuberculosis is the most closely related. 4.Low body mass index A low body mass index (BMI=weight/height2) (less than 20) is associated with increased risk of lung cancer. 5.Psychological factors Poor psychological adaptability, long-term mental depression, and significant type A personality (referring to fast action, impatience, aggressiveness and excitability) will increase the risk of lung cancer. 6.Kitchen fumes Lung cancer in women is more closely related to kitchen fumes. 7.Atmospheric pollution Where there are pollution sources (smelting, chemical, coking) within 500 meters around the residence 10 years ago, the risk of lung cancer will be increased. Occupational exposure to dust and asbestos dust will also significantly increase the risk of lung cancer. In addition, the effect of indoor pollution on lung cancer cannot be ignored. In addition to the above factors, regular physical exercise has a protective effect on lung cancer; early menarche and short menstrual cycle of women constitute risk factors for lung cancer.