Abstract: Objective: To observe bacterial biofilm formed by Haemophilus Influenzae in vitro.Methods: 11 strains of Haemophilus Influenzae were isolated from sputum collected from patients with AECOPD.Formation of bacterial biofilm was examined by crystal violet assay and scanning electron microscope.Results: Striking differences were observed among strains with regard to the ability to form biofilm.Typical membrane-like structure formed by bacterial cells and extracellular matrix was detected.Conclusion: Haemophilus Influenzae is capable to form bacterial biofilm in vitro,which related with pathogenesis of AECOPD.