To introduce the causes and clinical manifestations of obstructive sleep apnea hypoventilation syndrome (OSAHS) in children. To describe the effects of OSAHS on the organism of pediatric patients, to propose the key points of clinical diagnosis and treatment principles of OSAHS, and to evaluate the prognosis. Obstructive sleep apnea hypoventilation syndrome (OSAHS) in adults has been more widely recognized, but OSAHS in children has not received sufficient attention. Basic principles of diagnosis and treatment of OSAHS in children 1. However, the diagnosis is not clear based on history and physical examination alone. For example, severe snoring does not necessarily mean the presence of OSAHS, and enlarged tonsils and adenoids do not necessarily mean the presence of OSAHS. Polysomnography (PSG) is still the gold standard for definitive diagnosis. PSG is recommended when available. PSG is recommended for severe patients, especially those with other comorbidities, to clarify the severity of the condition and to fully understand the condition before treatment. However, if the patient’s condition is urgent, such as combined with respiratory or heart failure, it is not necessary to do PSG test first. 2.Treatment Tonsil adenoidectomy is the most important treatment measure. The surgical cure rate is 75%-100%. It is recommended that surgery be performed under general anesthesia with transoral intubation, and that the adenoids be scraped out completely under direct nasal vision using a nasal endoscope or otoscope. Risk factors for complications include age less than 3 years, AHI ≥ 10 times/h, developmental disorders, combined pulmonary heart disease or neuromuscular disease, and craniofacial developmental malformations. Those who are not suitable for surgery or failed surgery can be treated with continuous positive pressure ventilation (CPAP). Some patients require orthodontic treatment. Follow-up is performed after surgery, and PSG must be reviewed in severe patients.