Objective To observe the effect of shoulder-high head back-up position on airway ob-struction and hypoxia during fiberoptic bronchoscopy under non-intubated general anesthesia.Methods A total of 170 patients undergoing painless fiberoptic bronchoscopy,97 males and 73 females,aged 18-64 years,BMI 18.5-28.0 kg/m2,ASA physical status Ⅰ-Ⅲ,were randomly divided into two groups by ran-dom number method:observation group(group D,n=84)and control group(group C,n=83).Group D adopted the shoulder-high head back-up position,and group C adopted the supine position.All the pa-tients received intravenous general anesthesia of propfol combined with sufentanil,and were oxygenated via an ordinary endoscopic mask with an oxygen flow rate of 8-10 L/min.Fiberoptic bronchoscopy was per-formed when the modified observer assessment of alertness and sedation(MOAA/S)score was≤1 point.The number of cases in which hypoxia occurred and corrective measures were taken were recorded.The changes of HR,SBP,DBP,and SpO2 before induction of anesthesia(T1),1 minute after induction of an-esthesia(T2),endotracheal surface anesthesia(T3),at the time of examination(T4),and at the end of the examination(T5)were recorded.The degree of obstruction of the retropalatal space and retroglossal space at T2 were recorded.The level of glottic exposure and operating comfort of the endoscopist were recor-ded during the examination,and the incidence of postoperative neck discomfort,postoperative headache,postoperative dizziness,and nausea and vomiting were recorded.Results Compared with group C,the in-cidence of intraoperative moderate hypoxia,severe hypoxia,jaw support,and assisted ventilation was signifi-cantly decreased in group D(P＜0.05).Compared with T1,the HR were significantly increased at T3 and T4(P＜0.05),SBP and DBP were significantly decreased at T2,T4,and T5(P＜0.05),SpO2 was sig-nificantly increased at T2 and decreased at T4 in the two groups(P＜0.05),and SpO2 in group C was sig-nificantly decreased at T3(P＜0.05).Compared with group C,SpO2 was significantly increased at T4,the incidence of non-obstruction in the retrolingual space was significantly increased,and the incidence of com-plete obstruction in the retrolingual space was significantly decreased at T2,and the incidence of good glottic exposure was significantly increased,the incidence of poor glottic exposure was significantly decreased,and the incidence of good operating comfort of the endoscopist was significantly increased in group D(P＜0.05).There was no significant difference in the incidence of postoperative adverse events between the two groups.Conclusion Shoulder-high head back-up position can alleviate airway obstruction and reduce the incidence of hypoxia during fiberoptic bronchoscopy under non-intubated general anesthesia.