The occurrence of esophageal cancer is a gradual process, and in the process of carcinogenesis, there must be one main factor and several secondary factors, which play a synergistic role of promoting cancer in the process of carcinogenesis. Through a lot of investigations and researches in China and the world, it is believed that there are two main factors: one is due to the change of dietary structure and living habits, a large amount of acidic food is consumed, and the body is acidified, and the cancer cells will not die like normal cells due to the acidification of environment. Cancer cells do not die like normal cells due to the acidification of the environment. In fact, cancer cells are normal cells that take the initiative to mutate in order to grow in an acidic environment and continue to stretch out. There are two kinds of theories for the creation of cancer cells, one is the hypoxia theory of Dr. Gulberg of Germany, and the other is the acidic body theory of Japan’s Aiha. Dr. Gulberg’s theory points out that a healthy cell in a hypoxic environment can turn the cell into a cancerous cell, and the acidification of body fluids leads to the decline in the amount of dissolved oxygen, which was proved by experiments and won him the Nobel Prize. Aiha’s theory mentions that cells that become weakly alkaline usually die in the vicinity of the accumulation of acidic wastes, but there are cells that change their chromosomes in order to survive in an acidic environment, which is the beginning of cancer. Another external factor: (1) chemical substance factor, (2) toxic contamination, and (3) mental factor are also important reasons for the development of this disease. Among the two factors, internal factors play a decisive role, and the acidification of the body provides a good space for the survival and growth of cancer cells. Factors related to the development of esophageal cancer (1) The development of esophageal cancer is mainly related to the following five points: (1) Nitrosamines: Nitrosamines are a kind of strong carcinogenic substances. Studies have shown that residents who consume sauerkraut in Linxian County, a high prevalence area of esophageal cancer, have methylbenzylnitrosamines, nitrosopyrrolidines, and nitrosoguanidines induced by esophageal cancer in their gastric fluids and urines. And it was found that the amount of sauerkraut consumption and the incidence of esophageal cancer were positively proportional. (2) Injury of esophageal mucosa: Long-term favorite hot food, coarse food, drinking strong tea, eating chili peppers and other stimulating food can cause damage to esophageal mucosa, causing hyperplasia of esophageal mucosa, which may be one of the cancer-causing factors. Smoking and drinking strong alcohol have a certain relationship with the development of esophageal cancer. Various kinds of chronic esophagitis may be precancerous lesions of esophageal cancer. (3) Mold carcinogenic factors: The use of moldy food can induce precancerous lesions or squamous epithelial carcinoma in the esophagus and stomach of mice. This type of mold has a synergistic effect with nitrosamines in promoting cancer. (4) Trace elements and malnutrition: Serum molybdenum, hair molybdenum, urinary molybdenum and molybdenum in esophageal cancer tissues are all lower than normal in the population of esophageal cancer high incidence areas. There is a lack of molybdenum in the soil and water in the high incidence area of esophageal cancer in Linxian County, and the cancer inhibitory effect of molybdenum has been confirmed by most scholars. Malnutrition, insufficient intake of animal protein and vitamin AB2C deficiency are the common features of the diets of the residents in the high incidence areas of esophageal cancer, but most of the high incidence areas of malnutrition do not have a high incidence of esophageal cancer, so this is unlikely to be a dominant factor. (5) Genetic factors: Esophageal cancer has a significant family aggregation phenomenon, and it is common to see families with the disease of three or more consecutive generations in the high incidence areas, but esophageal cancer is not hereditary, and is closely linked with the dietary habits of the family. However, esophageal cancer is absolutely not hereditary, but is closely related to family dietary habits. (2) Etiology: It is believed that the development of esophageal cancer may be related to the following factors: (1) Dietary habits: Long-term smoking, drinking strong alcohol, eating hot food for a long time, eating too hard food and chewing too little, etc. have a certain relationship with the occurrence of esophageal cancer. 2.Carcinogenic substances (1) Nitrosamines: Nitrosamines are a group of strong carcinogenic substances. Residents of Linxian County, Henan Province, a high incidence area of esophageal cancer, like to eat sauerkraut, which contains nitrosamines. It has been proved that the amount of sauerkraut consumed is directly proportional to the incidence of esophageal cancer. (2) Mold: some people in China have induced esophageal cancer by feeding moldy food to rats for a long time. Genetic factors: The susceptibility of human population is related to heredity and environmental conditions. Esophageal cancer has significant family aggregation phenomenon, and it is not uncommon to see families with esophageal cancer patients in high incidence areas with three or more consecutive generations. Pre-cancerous lesions and other disease factors such as chronic esophageal inflammation, esophageal epithelial hyperplasia, esophageal mucosal injury, Plummer-Vinton syndrome, esophageal diverticulum, esophageal ulcers, esophageal leukoplakia, esophageal scar stenosis, hiatal hernia, pancreatic achalasia, etc., are all regarded as pre-cancerous lesions or pre-cancerous diseases of esophageal cancer. Nutrition and trace elements Dietary deficiencies of vitamins, proteins and essential fatty acids can make the esophageal mucosa hyperplasia and mesenchymal degeneration, which can further cause cancer. Lack of trace elements such as iron, molybdenum and zinc is also related to the occurrence of esophageal cancer. （Early esophageal cancer can be classified into latent type (not easy to be detected by naked eyes, but confirmed under microscope), erosive type (mild erosion of mucous membrane), plaque type (plaques of varying sizes in the mucous membrane, obvious thickening of mucous membrane at the place of cancerous lesion), papillary type (tumors appearing in the form of nodules, papillae or polyp-like elevations, with the edges and surrounding mucous membranes clearly demarcated).