【Abstract】 Objective To investigate the effect of preoxygenation 15 min preanesthesia combined highflow oxygen infusion prevention of hypoxemia during ERCP in elderly patients with bile duct stones under intravenous anesthesia. Methods The elderly patients with bile duct stones visited the general surgery ERCP diagnosis and treatment center of lanzhou university first hospital from March 2018 to October 2018 were randomly divided into the control group and the experimence group. Intraoperative lowflow (2L/min) oxygen in the control group. The experimence group received preoxygenation 15 minutes before anesthesia combined with intraoperative highflow (5L/min) oxygen. The changes of intraoperative oxygen saturation (SpO2), the incidence and severity of hypoxemia, operation time and anesthesia recovery time were compared between the two groups. Results There were no significant differences in the baseline data between the experimental group and the control group in terms of age, gender, ASA classification, BMI, and comorbidities; the SpO2 in the experimental group was higher than that in the control group during anesthesia induction, microscopy and stone removal (P＜0.05). The incidence of hypoxemia in the control group was higher than that in the experimental group during anesthesia induction and stone removal (P＜0.05), and it was prone to severe hypoxemia. The recovery time of anesthesia was shortened in the experimental group (P＜0.05), but there was no significant difference in the operation time between the two groups. Conclusion Preoxygenation before anesthesia combined with highflow oxygen infusion can significantly reduce the incidence of hypoxemia in elderly patients with ERCP, so that the intraoperative oxygen saturation tends to be stable and shorten the postoperative anesthesia recovery time.