The cleanliness of the intestine is a key factor in determining the success or failure of colonoscopy. If there is still a lot of feces in the intestine at the time of examination, it will affect the access and observation, or even fail to complete the whole colon examination, or cause a missed diagnosis due to fecal cover-up. Therefore, it is important to prepare the intestinal tract for cleansing before the examination. The most common and reliable method is to take laxatives before the examination. The most commonly used bowel cleansing methods with good safety include oral polyethylene glycol electrolyte solution, magnesium sulfate, etc. At the same time, drink enough water to cleanse the intestine, and the bowel cleansing is standardized by watery stools. For those who are not satisfied with intestinal cleansing, it can be combined with colon hydrotherapy to achieve better intestinal cleansing effect and meet the needs of colonoscopy. In addition, some dietary preparation before the examination is also necessary to cleanse the intestine, 3 days before the examination, stop taking iron preparations and start to eat a low residue diet. The day before the colonoscopy, it is recommended to eat colorless, less dregs or liquid food, such as fish, eggs, milk, soy products, porridge, noodles, bread, bananas, winter melon, potatoes, etc. It is advisable to bring previous colonoscopy reports, X-ray films, pathology reports, etc. for the doctor’s reference. Do not bring cell phones into the examination room to avoid affecting the normal work of the instruments. Doing colonoscopy is not as scary as you think, no need to be overly nervous and anxious, you must relax. During the examination, the abdomen may feel distended and painful because the large intestine is usually closed and has several curved parts, so the doctor will inject some air into the mirror to facilitate the entry and observation, and pump out the air after the observation is finished.