Babies spitting up watery liquid may be mouth ulcers, improper feeding, surgical diseases and so on. 1. Mouth ulcers: after the baby grows mouth ulcers, because of the pain in the mouth, the baby is reluctant to swallow saliva, which can lead to the baby spitting up watery liquid. 2. Improper feeding: after the baby eats too much milk or swallows a lot of gas, it can also cause the baby to vomit watery liquid. After paying attention to the feeding method, most of them can be improved. 3. Surgical diseases: such as intestinal obstruction, intussusception, etc., can also cause babies to vomit watery fluid. There are many reasons for babies to vomit watery liquid, if the frequency of frequent, more liquid, need to be timely to the hospital to avoid dehydration, electrolyte disorders and other conditions, delaying the baby’s treatment.