A new type of layered zirconium phosphonate (zirconium glycine-N, N-dimethylphosphonate, abbreviated as ZGDMP), with functional group of -COOH, has been successfully prepared and characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). To confirm the effect of the functional group -COOH on the structure and properties of composites, a series of chitosan/zirconium phosphonate modified by n-butylamine (BA-ZGDMP) nanocomposite films were prepared by casting process. FTIR spectra suggested that strong interactions existed between BA-ZGDMP and chitosan matrix. Compared to neat CS film, tensile strength (sigma(b)) and elongation at break (epsilon(b)) of the nanocomposite film improved by 35.1% and 15.6%, respectively, with loading ratio of just 1.0 wt %. In addition, the BA-ZGDMP also improved the water resistance of the nanocomposites. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 1106-1113, 2011