During the COVID-19 epidemic, our national guidelines have suggested that surgical patients should wear a mask to decrease the potential transmission of COVID-19 in the operating room, as long as the condition allows. However, so far, there is no study to discuss the influence of wearing a mask on the ventilation and blood oxygenation status in patients of spontaneous breathing with supplementary oxygen through an anesthetic facemask. This is a before-after study in the same patient, and 10 healthy volunteers were recruited, by testing the arterial blood gas parameters at key time points before and after oxygen inhalation to evaluate the effects of two different supplementary oxygen methods (‘disposable medical mask + anesthetic facemask’ and ‘anesthetic facemask only’) on the oxygenation of subjects. Our data demonstrated whether wearing a disposable medical mask or not could effectively increase the oxygen supply of the subjects compared with the basic value before oxygen inhalation; however, compared with the group without mask, the arterial oxygen partial (PaO2) reduced significantly at each time points when subjects wearing a disposable medical mask. There was no significant difference in other parameters, and our data showed that age growth and smoking had no significant effects on the difference of PaO2 between the groups with and without masks. This study demonstrates effective oxygen supplementation through anesthetic facemask in subjects with spontaneous breathing who is wearing a disposable medical mask, whose pulse oxygen saturation and arterial oxygen saturation can reach 100% rapidly, and this provides a theoretical basis for the management of patients with disseminated respiratory diseases to wear masks in the operating room; however, the rate and amount of PaO2 increase are both decreased as compared to those who is not wearing a disposable medical mask during supplementary oxygenation. Whether this difference will affect the clinical outcome needs further study.