Objective To explore the effect of high-flow nasal cannula oxygen therapy(HFNC)combined with conventional therapy on blood gas analysis and pulmonary function in patients with acute exacerbation of bronchiectasis and type Ⅱrespiratory failure.Methods A total of 40 patients with acute exacerbation of bronchiectasis and type Ⅱrespiratory failure admitted to the Department of Respiratory and Critical Care Medicine,Guangxi Zhuang Autonomous Region National Hospital from July 2020 to January 2023 were selected as the study objects,and they were divided into traditional oxygen therapy group (20 cases) and HFNC group (20 cases) according to random number table method.The traditional oxygen therapy group was treated with nasal catheter,and the HFNC group was treated with HFNC.The changes of arterial blood gas analysis indexes(arterial partial pressure of oxygen[PaO2],arterial partial pressure of carbon dioxide[PaCO2]and Oxygenation index [PaO2/FiO2])were compared in the two groups before treatment,2 and 24 hours after treatment and before discharge.The changes of pulmonary function indexes(forced expiratory volume in one second[FEV1],the percentage of forced expiratory volume in one second [FEV1%],forced vital capacity [FVC],forced expiratory volume in one second/forced vital capacity [FEV1/FVC]) and modified British Medical Research Council (mMRC) dyspnea questionnaire scores before and after treatment were compared in the two groups.Results At 2 hours,24 hours after treatment and before discharge,the PaO2 and PaO2/FiO2 of two groups were higher than those before treatment in the same group,and the PaO2 and PaO2/FiO2 in the HFNC group were higher than those in the traditional oxygen therapy group,and the differences were statistically significant(P＜0.05).At 24 hours after treatment and before discharge,the PaCO2 of the traditional oxygen therapy group was lower than that before treatment of the same group,and the difference was statistically significant (P＜0.05).At 2 hours,24 hours and before discharge,the PaCO2 of HFNC group was lower than that before treatment in the same group,and the PaCO2 in the HFNC group was lower than that in the traditional oxygen therapy group,and the differences were statistically significant(P＜0.05).Before discharge,the FEV1,FEV1%,FVC,and FEV1/FVC in two groups were higher than those before treatment in the same group,and the FEV1,FEV1%,FVC,and FEV1/FVC in the HFNC group were higher than those in the traditional oxygen therapy group,and the differences were statistically significant (P＜0.05).Before discharge,the mMRC scores of two groups were lower than those before treatment in the same group,and the mMRC score in the HFNC group was lower than that in the traditional oxygen therapy group,and the differences were statistically significant(P＜0.05).Conclusion HFNC is effective in the treatment of patients with acute exacerbation of bronchiectasis and type Ⅱrespiratory failure.Compared with traditional oxygen therapy,HFNC can improve the blood gas analysis index and lung function index of patients faster and better,and alleviate the symptoms of dyspnea.