The failure of nutrients, especially fats, to be adequately absorbed by the small intestine for a variety of reasons, resulting in symptoms such as diarrhea, malnutrition, and weight loss, is called malabsorption syndrome. Most patients with malabsorption syndrome have diarrhea. The number of bowel movements ranges from a few to more than ten, and diarrhea and abdominal pain are the most prominent symptoms of the disease. Diarrhea is usually “steatorrhea”, which is characterized by a large amount of stool, light brown or yellow, gray, unformed, foul-smelling, with a greasy sheen or foamy surface, and the stool often floats on the surface of the potty because of the large amount of fat in the stool. Due to insufficient absorption, resulting in malnutrition, common weight loss, tiredness and fatigue. Causes: 1, pancreatic enzyme deficiency: chronic pancreatitis, pancreatic cancer, pancreatectomy, cystic fibrosis. 2, bile salt deficiency: bile duct infarction, decreased hepatic synthesis (such as chronic hepatitis, cirrhosis), Crohn’s disease, ileal resection, due to stagnation caused by the jejunal cell overgrowth (such as “blind loop” produced by surgery, diabetic autonomic gastropathy). 3, disaccharidase deficiency: lactose and other disaccharidases deficiency. 4, small bowel disease: extensive surgical resection (such as jejunal bypass surgery in obese people, post-traumatic), radiation enteritis, intestinal ischemia, abdominal orifice inflammatory diarrhea, Whipple’s disease, primary intestinal lymphoma, blood gammaglobulin is too low, herpes-like dermatitis, eosinophilic gastroenteritis, amyloidosis, dumping parasitosis, intestinal lymphatic dilatation, glucose and galactose malabsorption. 5, a number of defects in digestion and absorption: post-gastrectomy, glycosuria, endocrinopathy (Addison’s disease, hyperthyroidism, Zollinga-Ellison syndrome), carcinoid tumors, systemic mast cell disease, scleroderma. 6. Drugs: laxatives, colchicine, cholestyramine, p-aminosalicylic acid (PAS), neomycin.