For a three-week-old baby vomiting, if it is caused by indigestion or indigestible food, you can take oral medications to help gastrointestinal digestion, such as Gastrointestinal Digestive Oral Liquid or Shan Bai Digestive Compound, as well as oral medications such as Lactobacillus Granules or Mamia to adjust the child’s intestinal flora, which will help the child recover from the disease. If the vomiting is caused by viral or bacterial enteritis, the child should be treated with antiviral, cephalosporin or penicillin medications, and oral medications to help gastrointestinal digestion, as well as medications to adjust the child’s intestinal flora, in order for the child to recover from the symptoms. If the child vomits with obvious abdominal distension, while not exhausting, not defecating, do not exclude the surgical intestinal obstruction or intestinal overlap and other diseases, this situation is not effective, you need to take the child to the hospital for detailed examination, under the guidance of doctors for further treatment.