As a congenital heart disease with left-to-right shunt, atrial septal defect in babies may have no clinical manifestations, or it may be manifested by backward growth and development, more sweating, feeding difficulties, frequent colds, excessive sweating, shortness of breath after exercise, and so on. If the secondary foramen ovale type atrial septal defect is less than 5mm, there is no clinical manifestation, and it can only be detected during ultrasound examination; if the atrial septal defect is 0.5-1cm, a few children will show the above symptoms; if the atrial septal defect is more than 1cm, the symptoms will be more obvious. If the atrial septal defect is of the primary foramen ovale type, the clinical manifestations of the atrial septal defect are more obvious due to the combination of mitral and tricuspid regurgitation at the same time. Atrial septal defect is an abnormal passage between the left atrium and the right atrium, which can lead to higher pressure in the left atrium and lower pressure in the right atrium, resulting in left-to-right shunt, leading to an increase in pulmonary arterial blood flow, and the patient manifests increased respiration and frequent respiratory infections, which are related to the type of the atrial septal defect and the diameter of the atrial septal defect. Babies should be seen in specialized hospitals when atrial septal defects are detected.