Obstructive sensation or dull pain behind the sternum when swallowing dry food is one of the early and middle stage manifestations of esophageal cancer. The main symptom is progressive dysphagia. In the early stage, there may be only discomfort or blockage when swallowing, pain behind the sternum or discomfort behind the sternum when swallowing food. Preventing the occurrence of obstruction or dull pain behind the sternum when swallowing dry food is undoubtedly the most fundamental measure to control esophageal cancer. According to the multi-stage nature of the occurrence and development of esophageal cancer, i.e. initiation, promotion and evolutionary stages, from the viewpoint of etiology, pathogenesis and clinical medicine evolution, the prevention of the occurrence and development of obstruction or dull pain behind the sternum when swallowing dry food is divided into two levels of prevention. 1. Primary prevention Primary prevention, i.e. etiological prevention, is the fundamental way to reduce the incidence of esophageal cancer, which is closely related to the progress of epidemiological research and etiological research, and it is the most ideal method, but it is very difficult to carry out comprehensively at present. (1) Change the habit of liking moldy food: There is sufficient evidence that consumption of moldy food, especially sauerkraut, moldy nest and fish sauce, is one of the important factors in the incidence of esophageal cancer, therefore, the danger of such food to human health should be vigorously publicized so that the public will eat less or not, and at the same time encourage the planting of vegetables and fruits to increase the intake of fresh vegetables and fruits and supplement vitamin C. Change the bad eating habits, do not eat moldy food, and eat less or no sauerkraut. Improve water quality and reduce nitrite content in drinking water. Promote micronutrient fertilizers to correct soil deficiency of molybdenum and other micronutrients. Apply Chinese and Western medicines and vitamin B2 to treat esophageal epithelial hyperplasia to interrupt the cancer process. Actively treat esophagitis, esophageal leukoplakia, cardia laxa, esophageal diverticulum and other diseases associated with the occurrence of esophageal cancer. Surveillance of susceptible people, popularize cancer prevention knowledge and raise awareness of cancer prevention. (2) Mold prevention of food: moldy food contains a variety of carcinogenic toxins, so it is very important to actively carry out mold prevention and detoxification of food, especially the importance of mold prevention for home storage should be publicized. Generally, the moisture content of grain is below 13% to meet the requirements of mold prevention. Once the grain is found to be moldy, it should be diligently dried, picked when consumed, washed and treated with alkali several times, which can effectively reduce the intake of mycotoxins. 2.Secondary prevention For esophageal cancer, it is impossible to achieve primary prevention completely. Since the occurrence and development of esophageal cancer takes a long time, if early detection, early diagnosis and timely treatment can be achieved, especially to stop the development of precancerous lesions, it is a realistic and feasible method for tumor prevention at present. (1) Census: Patients in high incidence areas who are over 35 years old and have family history of esophageal cancer or esophageal epithelial hyperplasia are defined as high-risk groups and should be monitored with emphasis, and residents in high incidence areas of esophageal cancer who are over 35 years old should be censored as much as possible. The census is mainly based on esophageal reticulocytological examination, and endoscopic examination should be conducted as soon as possible when suspicious patients are found, in order to achieve early diagnosis. The early manifestations of esophageal cancer, such as “swallowing discomfort”, should be well known to the general public in the high incidence area, so that the patients can be seen earlier for early diagnosis and treatment. (2) Prevention of precancerous lesions: precancerous lesions of esophageal cancer mainly refer to heavy hyperplasia of esophageal epithelium, and the cancer rate of the untreated group is 7.4%; the cancer rate of the treated group: 2.5% in the anti-cancer B III tablet, 2.5% in the anti-cancer B III tablet and 2.5% in the anti-cancer B III tablet. The cancer rate in the untreated group was 7.4%; the cancer rate in the treated group was 2.5% in the anti-cancer B III group, 1.4% in the anti-cancer B tablet group and 2.3% in the tylorone group, which were significantly different from those in the untreated group and more people returned to normal than those in the untreated group.