Objective To investigate the effectiveness of noninvasive positive pressure ventilation( NPPV) in acute exacerbation of chronic obstructive pulmonary disease ( AECOPD) complicated with severe type Ⅱ respiratory failure.Methods 37 patients who were admitted fromJanuary 2008 to June 2009 due to AECOPD complicated with severe type Ⅱ respiratory failure and had received NPPV therapy were enrolled as a NPPV group. Another similar 42 cases who had not received NPPV therapy served as control. All subjects received standard medication therapy according to the guideline. Arterial blood gases before and after treatment, the duration of hospitalization and intubation rate were observed. Results The arterial pH, PaO2 ,and PaCO2 improved significantly after treatment as compared with baseline in both groups ( P lt; 0. 05) .Compared with the control group, the average duration of hospitalization was significantly shorter ( 10 ±5 vs.19 ±4 days, P lt;0. 05) and the intubation rate was significantly lower ( 2. 7% vs. 16. 7% , P lt;0. 05) in the NPPV group. Conclusion The use of NPPV in AECOPD patients complicated with severe type Ⅱ respiratory failure is effective in improving arterial blood gases, reducing the duration of hospitalization and intubation rate.