To obtain an antibacterial chitosan derivative, composite films of N,O-Carboxymethyl Chitosan (N,O-CMCS) and bamboo fiber were prepared. A water-soluble chitosan derivative-N,O-CMCS was synthesized from chitosan with chloroacetic acid in alkaline solution. Composite films with 1-5 wt % N,O-CMCS content were prepared in NaOH/urea/thiourea solution. The DS of N,O-CMCS reached 1.70 and the water solubility increased with the increasing of DS. The carboxymethyl group was introduced into chitosan, which led to the decrease of thermal stability and crystallinity. The structural characterization confirmed that N,O-CMCS was adsorbed on the surface of bamboo fiber. The antibacterial performance of the composite films were enhanced with the increasing of N,O-CMCS content. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39851.