Objective To observe whether nasal mask airway can prevent or reduce the occurrence of hypoxemia during gastroscopic anesthesia by comparing with nasal catheter. Methods A total of 180 patients who were scheduled for gastroscopic anesthesia were enrolled. According to the random number table method, they were divided into two groups: a nasal cannula group (NC group, n=86) and a nasal mask airway group (NMA group, n=94). Before anesthesia, patients in both groups were inserted with nasal catheter or nasal mask airway and inhaled pure oxygen for 3 min. After administration with sufentanil (0.05 μg/kg) and propofol (2 mg/kg) for anesthesia induction, gastroscopic examination was performed when the Observer's Assessment of Alertness/Sedation (OAA/S) was 1 point. Their general information, gastroscopic duration and propofol dosage were recorded. The total incidence of hypoxemia, including mild to moderate hypoxemia (75%