With the current improvement in surgical techniques, the requirements for age and weight of the child have been gradually reduced, and children of any age and weight can undergo surgery if their condition requires it. However, there is still a great difference in the risk of surgery for children of different ages and weights. On the issue of timing of surgery for congenital heart disease, two factors are generally considered: on the one hand, the disease, the later the surgery, the heavier the progress of the disease, the worse the surgical results; on the other hand, the patient’s problem, the later the surgery, the older the child, the stronger the resistance, the safer the surgery. So the best timing of is the result of the combination of these two balance. To sum up, for children with mild disease, it is safer to wait until about 1 year old for surgery, while the more severe the disease, the earlier it should be done to avoid losing the chance of surgery or serious complications. For common conditions such as atrial septal defect, ventricular septal defect, patent ductus arteriosus, and pulmonary valve stenosis, surgery can be performed around 1 year of age. The common tetralogy of Fallot is generally considered appropriate between the age of 4 months and 1 year, but it also depends on whether the child has frequent hypoxic episodes, which must be done early if they are frequent or can be done when he/she is a little older if they are rare. The following diseases should be operated as soon as they are detected: 1. Pre-existing heart diseases that are likely to cause pneumonia and heart failure, such as giant ventricular septal defect, coarctation, complete pulmonary vein ectopic drainage, complete endocardial cushion defect, and main pulmonary septal defect. 2, Pre-existing heart disease causing hypoxic episodes such as severe tetralogy of Fallot, severe pulmonary valve stenosis. 3, Precardiac diseases causing hypoperfusion hypoxic acidosis such as hypoplastic left heart syndrome, interrupted aortic arch, and severe aortic constriction. 4, Arterial catheter-dependent precardiac disease such as pulmonary atresia with intact ventricular septum, transposition of the great arteries with intact ventricular septum, etc.