Polystyrene coated with gold nanoshell composite particles, with good photothermal properties, were prepared by electrostatic self-assembly. Firstly, polystyrene (PS) microspheres were synthesized by emulsifier-free emulsion polymerization, and it is determined that the PS microsphere has an average diameter of 165 nm, carboxyl on the surface, and its surface potential turned into +38.3 mV after modified by polyallylamine hydrochloride (PAH). Secondly, gold seeds, with an average diameter of 5.14 nm and surface potential of -10.7 mV, were prepared via sodium borohydride reducing chloroauric acid. Then, gold seeds were adsorbed on the surface of PS microspheres by electrostatic self-assembly and the composite particles were obtained after gold seeds grew multiple times. Finally, 0.3 mg/mL composite particles dispersion was irradiated with a near-infrared (NIR) light source and the temperature of the dispersion increased 13 degrees C after 5 min.