Monodisperse polymer microspheres P(St-AN) were prepared through two-steps polymerization stabilized with polymerizable anion-charged monomer Sodium Styrene Sulfonate (NaSS). The influence of acrylonitrile dropping time on particle size and dispersity were discussed. Using the P(St-AN) particles as template, raspberry-like Ag/P(St-AN) composites were obtained by chemical deposition. Composition, structure, morphology and catalytic performance of the composite particles were characterized by fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and UV-visible spectroscopic techniques. The results revealed that the P(St-AN) template particles were uniform spherical particles when the acrylonitrile were dropped 1~3 h after the reaction beginning. The particle size was between 600 nm and 800 nm. The obtained Ag/P(St-AN) were of uniform structure and Ag nanoparticles of face centered cubic crystal structure were well coated on the surface of the particles with good dispersity and stability. The Ag/P(St-AN) composite particles were used as the catalyst in 4-nitrophenol reduction to 4-aminophenol with NaBH4 as the reducer, and the reduction was significantly enhanced.