Gold nanoparticles-coated polystyrene (AuNPs-coated PS) composite particles with raspberry-like morphology are successfully prepared with the aid of a unique thermodynamically driving effect. It is of considerable interest that the AuNPs generate and self-assemble with raw, ordinary PS microspheres that preexist in the oxidation-reduction systems. The synthesized AuNPs-coated PS composite particles have been extensively characterized using scanning electron microscope, transmission electron microscope, and UV-Vis-NIR spectroscopy. The results indicate that the morphology of the resultant composite particles is governed by simply changing the amount and type of reductants and the concentration of PS microspheres. The AuNPs-coated PS composite particles also exhibit the good surface-enhanced Raman scattering and catalytic performances.