In this study, a chitosan nanoparticle dispersion solution as a novel multifunctional agent was developed to modify Antheraea pernyi silk. An ionization gelation methodology with chitosan and sodium tripolyphosphate (STPP) was used to prepare the chitosan nanoparticle solution, and then, Fourier transform infrared spectra, laser particle size analysis, and transmission electron microscopy (TEM) were used to characterize the structure and size distribution of the chitosan nanoparticles. The peaks at 3390.7, 1633.7, 1538.2, and 1258.1 cm(-1) revealed the reaction between the chitosan and STPP molecules in the chitosan nanoparticles. The average size of the nanoparticles in the aqueous dispersion solution was approximately 20 nm. TEM images clearly showed the round spherical morphology and the distribution of the particles in the solid state. The obtained chitosan nanoparticle dispersion solution was then applied to treat silk filaments and fabric. The results indicate that the surface of the chitosan-nanoparticle-treated A. pernyi silk fiber was rougher than that of the chitosan-treated and untreated ones, and a higher specific surface was achieved. In addition, the antibacterial activity, breaking strength, and wrinkle-resistance properties of the chitosan-nanoparticletreated A. pernyi silk fabric were also enhanced. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 3362-3369, 2010