Diarrhea has a cause and is divided into acute diarrhea and chronic diarrhea according to its etiology. Acute diarrhea is mostly caused by intestinal viral infections or bacterial and parasitic infections, others are drug poisoning, ulcerative colitis can also cause acute diarrhea. Chronic diarrhea mostly occurs from infectious diseases of the intestinal tract, such as chronic dysentery and intestinal tuberculosis. Diarrhea caused by non-infectious intestinal diseases is commonly caused by ulcerative colitis, Crohn’s disease, intestinal tumors, and small bowel hypokinesia, resulting in digestive malabsorption and intestinal hypokinesia, which can cause chronic diarrhea. After the occurrence of diarrhea, it is necessary to correct the disorders of water-electrolyte, acid-base balance and nutritional imbalance symptomatically, and supplement fluids appropriately.