The specific reasons why babies spit up after drinking milk are as follows: First, because the baby’s stomach is horizontal, it is easy to spit up, especially after drinking milk when parents do not give timely burping behavior or wait for digestion before lying down. Second, after the infant has eaten too much milk, it is easy to vomit after drinking milk because of the indigestion of the stomach and intestines. When babies add supplementary foods or suffer from gastrointestinal indigestion caused by viruses, bacteria and other disease factors, it is also easy for babies to spit up after drinking milk. The cause of vomiting should be clarified according to the time of occurrence, mental state and whether it is accompanied by indigestion such as bloating and diarrhea, so as to consider whether treatment is needed.