Objective To compare the efficacy and safety of humidified high-flow nasal cannula (HHFNC)and nasal continuous positive airway pressure (nCPAP) for moderate and severe bronchiolitis treatment in infants.Methods Thirty-two infants who were diagnosed as moderate and severe bronchiolitis admitted to Department of Pediatric Critical Care Medicine,the Affiliated Hospital of Qingdao University from September 2016 to May 2017 were selected,and they were randomly assigned into HHFNC group(17 cases) and nCPAP group(15 cases).The heart rate,breathing,oxygen saturation (SpO2),arterial partial pressure of oxygen [Pa (O2)],partial pressure of carbon dioxide [Pa (CO2)],pH value after treatment for 12 h,the duration of non-invasive ventilation and the incidence rates of invasive ventilation use,complications were compared between the 2 groups.Results After the treatment for 12 h,in HHFNC group,the heart rate was (130.88 ± 2.87) times/min,respiratory rate was (37.35 ± 3.55) times/min,SpO2 was(97.06 ± 1.43)％,pa(O2) was (99.65-±8.07) mmHg,pa(CO2) was (35.88 ±4.27) mmHg,pH was 7.42 ± 0.03;while in the nCPAP group,the heart rate was (135.73 ± 6.29) times/min,respiratory rate was (41.40 ± 4.40)times/min,SpO2 was (96.00 ± 1.13) ％,Pa (O2) was (91.33 ± 9.45) mmHg,pa (CO2) was (40.13 ± 3.72)mmHg,pH was 7.39 ± 0.03.The breathing,heart rate,oxygen saturation and arterial blood gas in both groups after treatment were improved significantly compared with those before treament,and the differences were statistically significant (all P ＜ 0.05);after treatment for 12 h,the heart rate,breathing,oxygen saturation and arterial blood gas of HHFNC group were improved more than those of the nCPAP group,and the differences had statistical significance (all P ＜ 0.05).The duration of non-invasive ventilation was (45.88-± 6.49) hours in HHFNC group,and (49.33 ± 8.99) hours in nCPAP group,so there was no difference between the 2 groups (t =1.254,P =0.219).There was 12 cases (80.0％) of mild complication in nCPAP group and 5 cases(29.4％) in HHFNC group,while the incidence rate of invasive ventilation use was 3 cases(20.0％) in nCPAP group and 1 case (5.9％) in HHFNC group.Conclusion The efficacy and security of HHFNC on moderate and severe bronchiolitis are better than those of nCPAP,and it is recommended for clinical application widely.