A baby with significant diarrhea, sometimes with little urine, is a condition that mostly suggests that the baby may be dehydrated. The first step in dealing with this condition is to treat the cause and intervene in the baby’s diarrhea. Montelukast is often used to protect the intestinal mucosa, and probiotics can be taken orally after an interval of at least half an hour to regulate the micro-ecological environment of the intestine and help improve the stool properties. The most critical thing in the treatment of diarrhea in babies is the need to prevent dehydration and electrolyte disturbances. Because babies lose not only water but also electrolytes when they have diarrhea, under normal feeding conditions, the main supplement is also water, while the amount of electrolytes is relatively small, so rehydration salts are routinely needed to prevent dehydration. Rehydration salts are liquids with a certain tension that maintain a good osmotic pressure in the body. Generally, the amount of rehydration is decided according to how much diarrhea the baby has, and how much more he/she pulls and drinks.