Pediatric diarrheal disease is a disease caused by multiple pathogens and multiple etiologies. The majority of affected children are under 2 years of age, with a particularly high incidence in infants from June to November. The peak of diarrhea occurs mainly from June to September and from October to January each year. Summer diarrhea is usually caused by bacterial infections, mostly mucus stools with a fishy odor; fall diarrhea is mostly caused by rotavirus, with dilute watery or pasty stools, but without a fishy odor. The incidence of diarrhea is second only to acute respiratory infections, and the mortality rate is also high if treatment is not carried out in a timely and effective manner. An important cause of death is dehydration and electrolyte disturbances in the body caused by diarrhea. Infants and young children have poorly developed digestive system, less secretion of various digestive enzymes, lower vitality, poor tolerance of food cannot adapt to large changes in food substances and quantity, and because of rapid growth and development, relatively more nutrients are required, the digestive tract is heavily burdened and often under stress, making it easy for digestive disorders to occur. The acidity in the stomach is lower than that of adults, and the antibacterial ability is poor. Immunoglobulins and gastrointestinal SIgA in the blood are low, making them susceptible to intestinal infections. Pediatric diarrhea can be caused by non-infectious and infectious causes. 1, non-infectious causes are: physiological diarrhea, when the nutritional content of breast milk exceeds the physiological needs of children and the limits of digestive function, it will cause diarrhea in children; improper feeding can cause diarrhea, mostly in artificially fed children, due to irregular feeding, too much or too little amount or inappropriate food components, such as premature feeding of large amounts of starchy or fatty foods, sudden changes in food varieties or weaning; individual children are allergic or intolerant to milk or Allergies or intolerance to certain food components (such as lactose deficiency), diarrhea can occur after feeding; sudden changes in climate, abdominal cold to increase intestinal peristalsis; overheated weather to reduce the secretion of digestive juices, and due to thirst to eat too much milk, increasing the burden on the digestive tract, are prone to induce diarrhea. 2, infectious causes: divided into intestinal tract infection and intestinal tract infection. Intestinal infections can be caused by viruses, bacteria, fungi and parasites, the first two are more common, especially viruses. Viral infections are: (1) human rotavirus: the most common cause of diarrhea in infants and young children in autumn and winter; (2) norovirus: mostly affects children and adults and is not closely related to diarrhea in infants and young children. Bacterial infections: mainly infections caused by E. coli and B. dysenteriae. Pathogenic microorganisms enter the digestive tract with contaminated diet or water, and can also be transmitted through contaminated daily necessities, hands, toys or carriers. In addition, when suffering from otitis media, upper respiratory tract infection, pneumonia, urinary tract infection, skin infection, etc. or acute infectious diseases, diarrhea may accompany due to fever and the role of toxins from pathogens to disrupt the function of the digestive tract. Sometimes, pathogens from extraintestinal infections can infect the intestinal tract (mainly viruses) at the same time.