The purpose of this study was to modify the surface characteristics of a ventilation tube (VT) with polyethylene glycol (PEG) coating and to evaluate the effect on biofilm formation. VTs made of polyethylene were coated with PEG. Streptococcus pneumonia R6 strain was used and a crystal violet assay was carried out to measure the in vitro and in vivo biofilm formation of rats bearing VTs. In the in vitro experiment, the optical density of the uncoated VT was 0.34±0.09 and the optical density of the PEG-grafted VT was 0.22±0.06 (p<0.05). In the in vivo experiment, the optical density of the uncoated VT was 0.54±0.12 and that of the PEG-grafted VT was 0.32±0.13 (p<0.05). Scanning electron microscopy showed that surface modification, roughness and hydrophilic characteristics improved and biofilm formation decreased. The reduced biofilm formation on the VT may be explained by the alteration of surface tension and roughness induced by PEG coating.