Diarrhea in a 7-month-old baby indicates a change in the frequency and nature of the baby’s stool. In this case, the first thing to determine is what causes your child’s diarrhea, whether it is caused by infectious factors or whether your child’s diarrhea is caused by a digestive disorder. If a 7-month-old child has added more starchy or fatty foods, it can cause digestive disorders, so pay attention to whether the child has added unsuitable complementary foods. If your child has diarrhea after adding milk powder, you should also pay attention to whether or not you are allergic to milk powder, and make it clear that you should give your child deeply hydrolyzed protein or amino acid milk powder. If your child is recently taking antibiotics because of illness and has diarrhea during this period, you should pay attention to antibiotic-related diarrhea and give your child probiotics to regulate the intestinal environment. If your baby has long-term diarrhea, you should also pay attention to lactose intolerance caused by a decrease in lactase activity. Clearly having lactose intolerance can be improved by eating diarrhea formula or taking oral lactase. If the baby has diarrhea with more mucus, purulent material or even blood in the stool, bacterial infectious diarrhea should be considered, and a clear diagnosis of stool tests will require antibiotic treatment. If the child has a viral infection, such as rotavirus infection caused by pediatric fall diarrhea, because the stool is egg-flake soup-like, so the child should be given montelukast and probiotics, while supplementing oral rehydration salts to prevent the child from dehydration. In conclusion, when a 7-month-old baby has diarrhea, we still need to analyze the child’s symptoms to clarify what is causing it and then actively treat it.