0bjective To study the effect of bacterial infection on acute exacerbation of chronic obstructive pulmonary disease(AECOPD)，and to compare the airway inflammation caused by different isolated bacteria．Methods A total of 159 sputum samples were collected from AECOPD patients diagnosed according to GOLD 2004 standard，in which conventional culture and identification of bacteria was conducted．The patients with purulent sputa were divided into different groups according to bacteria separated．Levels of IL-6．IL-8 and TNF-α in sputum supernatant were assayed and compared in different bacteria groups．the purulent sputum without isolated bacteria group(NG)and normal control group(NC)． Results One hundred and twenty-nine strains of bacteria were isolated in 159 qualified sputa，including 26 strains of Klebsiella pneumoniae(KB)，21 strains of Hemophilus influenza(Hi)，17 strains of Pseudomonas aeruginosa(PA)，37 strains of Haemophilus parainflb~enzae(HP)(mixed infection not included)and 28 strains of other bacteria．Among of all samples，20 were double infection of Haernophilus parainfluenzae with another bacterium．Ninety-seven purulent sputa were collected．According to bacteria isolated，these sputa were divided into five groups，named HP(24 samples)，Hi(20 samples)，PA(16 samples)，KB(19 samples)and NG(18 samples)．Contrast to NC，concentration of IL-8 and TNF-α rose in sputa from which PA，Hi，KB were isolated(Plt;0．05)．The level increased much more in sputa from which PA and Hi were isolated compared with KB(Plt;0．05)．Concentration of IL-6 rose in sputa of each group collected from AECOPD patients contrast to sputa collected from NC(Plt;0．05)，without significant differences among all other group except for NC．Conclusions Bacterial infection plays an important role in AECOPD characterized with high level of inflammatory factors especially when PA，Hi，KB were infected bacteria．This study provides evidence for antibacterial therapy in AECOPD patients．