If a 3-month-old baby has diarrhea, if the diarrhea is not severe and there are no symptoms of infection poisoning, it is usually necessary to do a good job of managing the diet and properly choose drugs with few side effects and suitable for infants, usually the following categories: first, probiotics, which should usually be taken half an hour after feeding, with bifidobacteria, Saccharomyces boulardii dispersion and so on commonly used. Second, appropriate mucosal protective agents, usually montelukast on an empty stomach, etc. Third, dehydration should be prevented and corrected, and hypotonic oral rehydration salts are usually needed to prevent and correct dehydration. Fourth, should do a good job of dietary adjustment, change to a small number of meals, breastfeeding mothers should avoid greasy, irritating and allergy-prone food intake. Fifth, attention should be paid to good perianal and perineal skin hygiene to prevent secondary infections and diaper rash.