It is necessary to drink laxatives to do painless colonoscopy, such as: polyethylene glycol electrolyte dispersions, sodium phosphate oral solution, and so on. Drinking laxatives before doing painless colonoscopy is because of the need to clean up the intestinal tract, clean up the feces in the intestinal tract, in order to facilitate the examination of colonoscopy, which is conducive to the judgment of the disease. Generally 4-6 hours before the examination to start the oral laxative bowel preparation, there are two main types of laxatives to do colonoscopy, including electrolyte bulk and sodium phosphate oral solution, these two drugs are currently more common and more clinical applications, generally taking laxatives for about half an hour to have a bowel movement. The prerequisite is to take it according to the instructions, according to the doctor’s instructions, and to walk on the floor more often after taking laxatives, which can promote gastrointestinal peristalsis and can defecate. The criterion for better bowel preparation is the clear, watery appearance of the expelled feces. It should be noted that, in addition to oral intestinal drugs, in the one or two days before the colonoscopy, it is best to eat a light, soft, easy-to-digest food, avoid rough and indigestible food.