Octahedron-like CeO₂ particles assembled by nanosheets with exposed (001) facets have been successfully synthesized. It has been demonstrated that polyvinyl pyrrolidone (PVP) plays an important role in the formation of octahedral CeO₂ assembled by the nanosheets. The octahedral CeO₂ assembled by the nanosheets exhibit high CO oxidation activity due to their special structures.