Smoking has the possibility of digestive system diseases, cardiovascular diseases, respiratory system diseases, cancer and other hazards. 1. Digestive system diseases: long-term smoking is likely to lead to excessive secretion of gastric acid, inhibit pancreatic secretion of sodium bicarbonate, leading to increasing load on the duodenum, may induce duodenal bulb ulcers, gastritis and other diseases. 2. Cardiovascular diseases: long-term smoking may lead to heart disease, cerebrovascular disease and so on. 3. Respiratory diseases: long-term smoking may lead to inflammation of the respiratory mucosa, serious inflammatory secretion oozing, congestion, etc., and may also lead to chronic obstructive pulmonary disease, bronchitis, etc. 4. Cancer: Long-term smoking may cause bladder cancer, esophageal cancer, laryngeal cancer, lung cancer and so on. In addition to the above hazards, regular smoking will also affect the health of people around, such as regular inhalation of second-hand smoke may lead to increased incidence of lung cancer. It is recommended that smokers should go to the hospital regularly to check their lung function, and once a decline in lung function is detected, it is recommended to quit smoking as soon as possible for treatment.