Chitosan (CS)-poly(acrylic acid) (PAA) complex nanoparticles, which are well dispersed and stable in aqueous solution, have been prepared by template polymerization of acrylic acid (AA) in chitosan solution. The physicochemical properties of nanoparticles were investigated by using size exclusion chromatography, FT-IR, dynamic light scattering, transmission electron microscope and zeta potential. It was found that the molecular weight of PAA in nanoparticles increased with the increase of molecular weight of CS, indicating that the polymerization of acrylic acid in the chitosan solution was a template polymerization. It was also found that the prepared nanoparticles carried a positive charge and showed the size in the range from 50 to 400 nm. The surface structure and zeta potential of nanoparticles can be controlled by different preparation processes. The experiment of in vitro silk peptide (SP) release showed that these nanoparticles provided a continuous release of the entrapped SP for 10 days, and the release behavior was influenced by the pH value of the medium.