Patients should fast for more than 8-10 hours before gastroscopy, and if they undergo gastroscopy in the morning, it is better to eat some liquid food the day before, and try to avoid eating some green vegetables, fruits and foods rich in high fiber. Do not eat after dinner, likewise do not eat at breakfast, and then do not drink water. If you are having a gastroscopy in the afternoon, eat liquid, digestible food for breakfast and do not eat from noon onwards. If the colonoscopy is performed, the patient should also eat liquid and digestible food the day before, and try to avoid eating green vegetables, fruits, fatty vegetables and fruits and other foods with color, such as nori, kelp and other high-fiber foods that can be digested. The most important thing is to make sure that after drinking the laxative, the patient drinks a lot of water and walks around a lot, and finally make sure that the stool is free of sludge.