Diarrhea (diarrhea) is a group of gastrointestinal syndromes caused by multiple pathogens and factors, characterized by an increase in the number of stools and changes in stool properties. It is one of the most common diseases in infants and young children in China. Infectious factors include viral infections, bacterial infections, fungi, parasites, extra-intestinal infections and diarrhea caused by the use of antibiotics. 2. Non-infectious factors include dietary factors and climatic factors. Second, classification 1, according to the course of classification Acute diarrheal disease: the course of disease within 2 weeks; migratory diarrheal disease; the course of disease in 2 weeks-2 months; chronic diarrheal disease: the course of disease in more than 2 weeks. 2, according to the pathophysiological classification: osmotic diarrhea, secretory diarrhea, exudative diarrhea, malabsorption diarrhea 3, according to the etiological classification: infectious diarrhea, non-infectious diarrhea 4, according to the classification of the condition Light: no dehydration, no toxic symptoms; medium: mild to moderate dehydration or mild toxic symptoms; heavy severe dehydration, or obvious toxic symptoms (irritability, depression, pallor, high fever or body temperature not rise, white blood cell count significantly increased, etc.). Prevention and treatment of dehydration; (1) Prevention of dehydration. From the beginning of diarrhea, give sufficient oral fluids to prevent dehydration. Breastfed children should continue to breastfeed and increase the frequency of feedings and extend the duration of single feedings; mixed-fed infants should be given ORS or other clean drinking water on the basis of breastfeeding; non-breastfed (artificially fed) infants should be given ORS or food-based rehydration fluids such as soup, rice soup water and yogurt drinks or clean drinking water. It is recommended that a certain amount of fluid (<6 months, 50 ml; 6-2 years, 100 ml; 2-10 years, 150 ml; 10 years or more for children or adults who can drink as much as they can) be given after each loose stool until the diarrhea stops. (2) Mild to moderate dehydration. Correct dehydration promptly with oral rehydration solution by applying ORS, dosage (ml) = weight (kg) × (50-75), to be taken within 4 hours; observe the child's condition closely and counsel the mother to give the child ORS solution. The following conditions indicate possible failure of oral rehydration: ① persistent, frequent and massive diarrhea (>10-20ml/Kg.h), ② insufficient dose of ORS fluid, ③ frequent and severe vomiting; if nearing 4 hours, the patient still shows dehydration, adjust the rehydration plan; re-evaluate the child’s dehydration status after 4 hours, then choose the appropriate plan. 2.Continue feeding 3.Zinc supplementation therapy 4.Rational use of antibacterial drugs 5.Other treatment （1）Intestinal mucosa protector: such as montelukast: children <1 year old: 3g/d in 2 times, children >l year old: 3g/d in 3 times （2）Microecological therapy giving probiotics such as bifidobacteria, lactobacillus, etc. For antibiotic-related diarrhea, the application of Saccharomyces boulardii is recommended; （3）Vitamin A supplementation (4) antisecretory drugs: for secretory diarrhea. (5) Traditional Chinese medicine treatment: using evidence-based prescriptions, acupuncture, acupoint injection and tui-na.