Objective To investigate the preventive effect of rapid preoxygenation technique on hypoxia caused by respiratory depression during outpatient obstetrics-gynecology operations. Methods According to a computer-generated random sequence, a total of 120 ASA I-II patients undergoing outpatient obstetrics-gynecology operations were randomly allocated into the trial group or the control group, 60 in each group. Patients in the control group received preoxygenation with tidal volume breathing. Patients in the trial group received preoxygenation with eight deep breaths (DB) in 1 min before anesthesia. All patients were induced with midazolam 1 mg, fentanyl 1μg /kg and propofol 2 mg/kg, and were maintained with propofol when needed. The following parameters were observed, including the incidences of respiratory depression and apnea, the onset time of anesthesia, the total doses of propofol as well as the changes in PetCO2 and SpO2. Results No significant differences were observed in demographic characteristics, the onset time of anesthesia, the total doses of propofol, and the incidences of respiratory depression and apnea between the two groups (P gt;0.05). However, the SpO2 in the control group was decreased significantly with a higher incidence of hypoxia (Plt;0.05). Conclusions Rapid preoxygenation technique may increase the oxygen reserves and improve the tolerance to hypoxia. It is effective in avoiding hypoxia caused by respiratory depression and apnea during outpatient obstetrics-gynecology operations.