Objective To investigate the application effect of high-flow nasal cannula oxygen therapy(HFNC)in the treat-ment of acute exacerbation of chronic obstructive pulmonary disease(COPD).Methods Seventy patients with acute exacer-bation of COPD combined with respiratory failure admitted to Jiaocheng Branch of the First Hospital of Shanxi Medical Uni-versity from January 2021 to January 2023 were selected as the study objects,and were divided into control group(35 cases)and treatment group(35 cases)according to random number table method.All patients were given treatment such as infec-tion control,phlegm relief and cough relief,spasm relief and asthma relief,water and electricity balance maintenance,nutri-tional support,etc.The control group was given traditional oxygen therapy(nasal catheter oxygen or mask oxygen),and the treatment group was given HFNC.The changes of potential of hydrogen(pH),arterial partial pressure of oxygen(PaO2),arte-rial partial pressure of carbon dioxide(PaCO2),procalcitonin(PCT)and C-reactive protein(CRP)were compared between the two groups before and 72 h after treatment.Results After 72 hours of treatment,PaCO2,PCT and CRP in the treatment group were lower than those in the control group,while pH and PaO2 in the treatment group were higher than those in the control group,the differences were statistically significant(P<0.05).Conclusion HFNC is effective in the treatment of acute exacerbation of COPD combined with respiratory failure.It can improve the patient's respiratory function,reduce the inflammatory state.