Children’s sudden fainting and white lips may be related to hypoglycemia, vasovagal syncope and congenital heart disease. 1. Hypoglycemia: digestive energy is needed for the brain to function, and when there is insufficient blood sugar in the body and insufficient supply of energy to the organism’s brain, symptoms such as fainting, cold sweating, and whitening of the lips will occur. 2. Vasovagal syncope: it may be a variety of stimuli such as emotional tension and prolonged standing. Through the vagus nerve-mediated reflexes, it leads to vasodilation and slowing of heart rate, resulting in transient loss of consciousness due to cerebral hypoperfusion and hypoxia, which may be accompanied by symptoms such as pallor and cold sweat. The most common cause of unexplained syncope in pediatric period, according to incomplete statistics, about 80% of syncope belongs to this category. 3. Congenital heart disease: for example, aortic valve stenosis, commonly found in patients with severe stenosis. During exercise, due to insufficient cardiac excretion, resulting in insufficient blood supply to the myocardium. Symptoms such as sudden fainting and white lips occur. Children’s sudden fainting, white lips can also be seen in other causes, it is recommended to seek medical attention in a timely manner, comply with the doctor’s instructions to carry out relevant examinations, with the help of the doctor to clarify the cause, and targeted treatment or treatment.