Esophagus is mainly examined by upper gastrointestinal imaging, chest CT and gastroscopy. 1. Upper gastrointestinal imaging: After taking barium and iodine orally, a large amount of contrast agent enters the esophagus and attaches to the esophageal mucosa. Through changing the body position, we can observe the traveling of the contrast agent in the esophagus under the X-ray, and make clear the degree of smoothness of the esophageal wall. 2. Chest CT: Through thin-layer chest CT, the width of the esophagus and the surrounding lymph nodes are clarified in each section, and it is clarified whether the esophageal lesion is invaded or not and the situation around the esophagus. 3. Gastroscopy: Through gastroscopy, the growth of esophageal mucosa can be visualized, and the esophageal mucosa can be observed for ulceration, inflammation, bleeding, erosion, and the presence of malignant tumor proliferation.