A series of silver nanoparticles with good dispersion, controllable size and uniform size distribution were prepared by liquid phase reduction method with silver nitrate as precursor and P(AA-co-HEA) prepared in our laboratory as the stabilizing agent and reducing agent, respectively. The effects of neutralization degree of the copolymer, reaction temperature, composition and content of P(AA-co-HEA) on sizes of silver nanoparticles were investigated. The chemical composition and morphological structure of P(AA-co-HEA)/Ag nanocomposite sol were characterized by fourier transform infrared spectrometer (FTIR), transmission electron microscope (TEM), and so on. The antibacterial experiments show that the as-prepared nanocomposite sol has excellent antibacterial activities both to Escherichia coli and Staphylococci aureus.