(1) Middle-aged and elderly people aged 45-65. (2) People with poor dietary habits: those who like to eat hot, coarse and hard foods. (3) People with long-term intake of carcinogens such as nitrosamines and fungal toxins. (4) Smokers and alcoholics. (5) Those who have family history of tumor. (6) People with precancerous esophageal lesions and precancerous diseases: precancerous lesions such as esophageal epithelial hyperplasia with severe hyperplasia. Pre-cancerous diseases include chronic inflammation of esophagus, reflux disease, pancreatic dyschondroplasia and chemical burns of esophagus.