Objective To evaluate the preoperative value of the sleep respiration monitoring and upper airway obstruction positioning system ApneaGraph 200 (AG 200,JC Medical,America) in disease diagnosis (severity) and the location of upper airway obstruction plane in patients with obstructive sleep apnea hypopnea syndrome (OSAHS). Methods A total of 121 suspected patients with OSAHS were randomly selected. They were examined by Müller's maneuver in the upper airway obstruction site. Then they underwent one-night (7 h) sleeping monitor by polysomnography (PSG, D-22525, Weinmann GmbH, Germany) and AG 200 simultaneously. The data obtained by PSG and AG 200 were compared, including apnea-hypopnea index (AHI), mean arterial blood oxygen saturation (mean SaO₂, MSaO₂), lowest arterial oxygen saturation (lowest SaO₂, LSaO₂), percentage of the cumulative time of SaO₂≤90% to total monitoring time (CT90%) and diagnosis of the properties and the severity of upper airway obstruction. The constituent ratios of the different obstructive plane measured by AG 200 and the upper airway obstructive sites determined by Müller's maneuver were also compared. Results The AHI, MSaO₂, LSaO₂, CT90% and the properties and the severity of upper airway obstruction by the AG 200 and PSG were similar. The positive rates of the upper plane obstructive sites determined by the endoscopy with Müller's maneuver and AG 200 were the same. The positive rate of the down plane obstructive sites determined by AG 200 was significantly higher than that determined by the endoscopy with Müller's maneuver (P <0.05). Conclusion One-night PSG and AG 200 monitoring can simultaneously achieve accurate qualitative and primary positioning diagnosis of OSAHS. AG 200 can identify the level of upper airway obstruction more accurately when combined with the endoscopy with Müller's maneuver.