Objective To explore the clinical features and diagnosis of obstructive sleep apnea hypopnea syndrome (OSAHS) in children, and to analyze the characteristics of polysomnography. Methods Lateral cephalometric radiography, fiberoptic nasopharyngoscopy and sleep apnea monitoring were performed in 49 children suspected of OSAHS by medical history and routine physical examination. Results Most of the children had a clear history of snoring, breath-holding, and upper airway narrowing caused by tonsil and adenoid hypertrophy. Polysomnography (PSG) was used to monitor 41 cases, including 1 case of simple snoring, 5 cases of upper airway resistance syndrome, and 35 cases of OSAHS; the other 8 cases were diagnosed as OSAHS by Autoset I monitoring. Conclusion The clinical manifestations of OSAHS in children differed somewhat from those of adults, with obstructive hypoventilation accompanied by varying numbers of apneic episodes, Staged hypovolemia is the main feature, there is no obvious sleep structure disorder, respiratory disorders are generally not accompanied by the occurrence of microarousal, PSG is an important means of identifying sleep-related respiratory disorders in children.