To observe the effect of noninvasive positive pressure ventilation combined with doxofylline injection on the improvement of clinical symptoms，the lung function and the inflammatory responses in patients with chronic obstructive pulmonary disease(COPD)complicated with respiratory failure.Methods：A total of 130 cases of patients with COPD complicated with respiratory failure treated in the Respiratory Department in our hospital were included in the study，and were randomly divided into two groups，65 cases in each group.The control group was given noninvasive positive pressure ventilation，and the observation group was additionally treated with doxofylline injection based on the treatment of the control group.The clinical effect and the improvement of clinical symptoms after treatment in the two groups were detected，and the blood gas indexes，the lung function indexes and the levels of inflammatory factors before and after treatment in the two groups were detected.Results： After treatment， the remission time of cough and expectoration，dyspnea，wheezing and moist rale in the observation group was obviously shortened when compared with that in the control group，and the total clinical effective rate was improved，differences being significant(P＜ 0.05).During different periods of the treatment，the levels of PaO2，FVC，FEV1，FEV1/FVC and MVV in the observation group were higher than those before treatment and those in the control group in the same period，while the levels of PaCO2，CRP，PCT，TNF-α and IL-17 were obviously lower than those before treatment and those in the control group in the same period，differences being significant(P＜0.05).Conclusion：The therapy of noninvasive positive pressure ventilation combined with doxofylline injection can promote the improvement of clinical symptoms，improve the lung function as well as oxygen saturation and reduce inflammatory responses，is conducive to the clinical treatment of patients with COPD complicated with respiratory failure，and better than simple noninvasive positive pressure ventilation.