Background: Chronic obstructive pulmonary disease (COPD) is a progressive disease, it is worse by time and interupted with acute exacerbation. The most common cause of COPD is bacteria infection. Objective: Research on bacteria features of acute exacerbation of chronic obstructive pulmonary disease. Patients: 100 patients were diagnosed as acute exacerbation of COPD who were treated as inpatients in Respiratory centre, Bach Mai hospital. Method: Retrospective. Results: mean age: 67 +/- 9.5 year old. Male: 90 percent, female: 10 percent. Smoking: 76 percent. Bacteria was found at 22/100 (22 percent) cases. Acinetobacter baumanni: 12/22 patients, Klebsiella pneumoniae: 5/22 patients, Pneumoniae aeruginosa: 4/22 patients, Acinetobacter junnii: 1/22 patient. No significant relation between bacteria infection and severity classification as Anthonisen (p0.05). Conclution: Proportion of bacteria finding was not high. The most common bacteria was the pathogen which have highest resistant features in Vietnam.