Poly(ethylene terephthalate) (PET)/clay nanocomposite was prepared by the direct polymerization with clay-supported catalyst. The reaction degree of catalyst against the cation exchange capacity of clay was 8 wt%. The intercalation of PET chains into the silicate layers was revealed by X-ray diffraction studies. SEM morphology of the nanocomposite showed a good dispersion of clay-supported catalyst, ranging from 30 to 100 nm. The intercalated and exfoliated clay-supported catalyst in PET matrix was also observed by TEM. The improvement of O-2 permeability for PET/clay-supported catalyst composite films over the pure PET is approximately factors of 11.3-15.6. (c) 2006 Wiley Periodicals, Inc.