An atrial septal defect is an abnormality in the primitive atrial septum during embryonic development, resulting in a hole left between the left and right atria. Atrial septal defects are divided into secondary foramen ovale and primary foramen ovale defects. The more frequent clinical cases are secondary septal defects, which are caused by the abnormal separation of the original atria, leaving an unclosed atrial foramen between the left and right atria, accounting for 6% – 10% of congenital heart disease. Most children are asymptomatic in infancy, but in childhood they may present with shortness of breath after activity, reduced activity tolerance, developmental delay, and susceptibility to respiratory infections. In adults, pulmonary hypertension, arrhythmia and congestive heart failure can occur, and the risk of surgery is greater than in children. Therefore, all children with clinical symptoms and pulmonary circulation volume: body circulation volume >1.5:1 should be treated surgically or interventionally (placement of blocker), and the age of surgery is preschool. 1.Interventional treatment: above 3 years old, those with central atrial septal defect, diameter less than 36 mm, left ventricular side atrial defect edge from the upper and lower vena cava greater than or equal to 7 mm, right ventricular side atrial defect edge from the upper and lower vena cava greater than or equal to 5 mm, can be treated with interventional treatment, atrial septal defect blocker to block the defect. Interventional treatment has the advantages of less trauma, lower complications, no blood transfusion and shorter hospital stay compared with surgical treatment. 2.Surgical treatment: Those who do not meet the above-mentioned interventional indications and those with pulmonary hypertension or other combined intracardiac malformations (such as pulmonary vein ectopic drainage) should be treated by open-heart surgery. The defect is repaired by direct suturing or patching with the assistance of extracorporeal circulation through a median sternal incision. 3.Medical treatment: including anti-heart failure and cardiac arrhythmia, etc. Attention needs to be paid to the prevention and treatment of respiratory tract infections.