Abstract: Polystyrene (PS) microsphere prepared by soap-free emulsion polymerization was coated with C_eO₂ by chemical precipitation. As-prepared samples were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), field emission scanning electron microscopy (FESEM), energy dispersive analysis of X-rays (EDAX). Thermal oxide film on top of silicon wafer was polished by PS/C_eO₂ composite abrasives. The polished silicon wafer surface by novel composite abrasives was characterized by atomic force microscopy (AFM). The results indicated that core-shell PS/C_eO₂ composite particles with the diameters of 250~300 nm possessed a 10~20 nm thin shell that was composed of uniformly packed C_eO₂ nanoparticles (particle diameter of 5~10 nm). Ra and RMS (root-mean-square) within 5 μm×5 μm area of thermal oxide film surface polished by PS/C_eO₂ composite abrasives were 0.188 nm and 0.238 nm, respectively. The material removal rate was 461.1 nm/min.