Abstract: Objective： To explore the efficacy and safety of supraglottic jet ventilation for patients undergoing colonoscopy supported by monitored anesthesia care (MAC). Methods： Forty-nine patients scheduled for painless colonoscopy were randomly divided into two groups: the control group utilizing routine passive oxygen supply with nasal cannula (n=24) and the supraglottic jet ventilation (SJV) group utilizing active oxygen supply with manual jet ventilator (n=25). Anesthesia was induced and maintained by intravenous injection of propofol. HR, BP, and SpO₂ were continuously monitored. Results： There was no significant difference regarding height, weight, age, and body mass index (BMI) between the two groups. The averaged lowest and highest SpO₂in SJV group were significantly higher than those in the control group (P=0.01). Degree of thoracic lifting movement in SJV group was significantly higher than that in control group (P=0.03). There was no significant difference regarding the times for using facial mask ventilation, the propotion of time for maintaining SpO₂ above 96%, average PetCO₂ during the procedure, or complications between the two groups. Conclusions： SJV can provide adequate oxygen supply for patients undergoing painless colonoscopy without obvious complications.