Pediatric lactose intolerance is a common and frequent disease in pediatric internal medicine clinics, and the etiology of pediatric lactose intolerance is clinically divided into primary and secondary, of which the correlation between pediatric lactose intolerance and pediatric diarrhea is getting more and more attention in the clinic. The correlation between pediatric lactose intolerance and pediatric diarrhea is divided into three cases: 1. Pediatric diarrhea, especially autumn diarrhea, can lead to damage to the epithelial cells of the small intestine, resulting in a temporary depression of gastrointestinal function, causing a decrease in lactase secretion or activity, which in turn leads to the occurrence of pediatric lactose intolerance. 2. During the period of diarrhea in children, they continue to drink milk powder or fresh milk and other dairy products, thus increasing the burden on the intestinal tract, which will also lead to the occurrence of lactose intolerance in children. 3, during the period of diarrhea in children, high doses of cephalosporin antibiotics, etc., some children will occur lactose intolerance. Only by fully understanding the correlation between pediatric lactose intolerance and pediatric diarrhea can parents of children with diarrhea be properly guided on how to care for and treat them, thus reducing the incidence of pediatric lactose intolerance.