1, too little fiber in the diet, or the amount of food is too small, the gastrointestinal tract can not produce effective stimulation, gastrointestinal peristalsis slowed down, resulting in constipation. 2, the gastrointestinal tract obstruction, its contents can not pass normally, stagnant in the stomach or intestinal tract constipation, such as pyloric obstruction, intestinal obstruction, which the elderly pay special attention to tumor-induced obstruction or stenosis to produce constipation. 3, colonic stress function is reduced. Under normal circumstances, the colon contents can stimulate the colon to cause peristalsis, when the colon, especially the rectum stress decompensation, although the feces into the rectum can not cause stool and defecation action. It is common in elderly people who take oral laxatives for a long time, or in young people who work under stress and ignore the need to defecate. Another hyperthyroidism, high blood calcium can also cause constipation. 4, when there are anal diseases such as: anal fissure, hemorrhoids, perianal abscess, etc., because of the painful defecation, and do not dare to defecate caused by constipation, also known as defecation difficulties. 5, mental factors, excessive mental tension or depression, inhibit the natural defecation reflex, can produce and develop into serious constipation. 6, some extra-intestinal diseases can also cause constipation, such as: hypokalemia, hypothyroidism, paroxysmal disease, etc. 7, long-term oral administration of some drugs can also produce constipation, such as gastric mucosa protective agents: Similac, Lizudra, etc., and antihypertensive drugs such as calcium ion antagonists. When constipation occurs, pay attention to further examination of blood routine, stool routine plus occult blood, and thyroid function, in addition to gastrointestinal motility test, fecal imaging or colonoscopy.