You can eat low-slag and easy-to-digest foods the day before the gastroenteroscopy and avoid foods rich in crude fiber. You can eat low residue and easy-to-digest food for breakfast and lunch the day before the gastroenteroscopy, such as white porridge, noodles, steamed buns, fish, eggs and tofu. Avoid foods rich in crude fiber, such as vegetables with stems and leaves, meat, corn, kelp, nori, etc. Also avoid fruits with colors and seeds, such as watermelon, tomatoes, kiwi, etc., which may obscure the colonoscopic view. Eat your dinner the day before the gastroenteroscopy before 6:00 p.m. You can eat a semi-liquid or liquid diet, such as thin rice, steamed eggs in water, and lotus root powder. No food will be eaten after six o’clock until the end of the gastroenteroscopy. Keeping the intestinal lumen clean is the foundation of high-quality colonoscopy operation. Bowel preparation that does not meet the cleanliness requirements will affect the diagnosis and treatment under colonoscopy and the therapeutic effect. So be sure to complete the bowel preparation carefully under the guidance of professional doctors.