Abstract: Nanoscale powders of CeO_2 and Al_2O_3 were prepared via homogenous precipitation method. The polishing slurry for the chemical-mechanical-polishing of silicon wafer was prepared from the resulting nano-particulates, keeping the mass fraction of the nano-particulates therein as 1%. Thus the polishing tests with respect to the single crystal Si wafers in the presence of the polishing slurry containing the nano-particulates were carried out to investigate the polishing effect. The morphologies and surfaces roughness of the polished Si wafers were observed and determined on an atomic force microscope. It was found that the nano-CeO_2 was superior to nano-Al_2O_3 in terms of the ability to reach ultra-precise polishing of the Si wafers, which could be related to the relatively smaller hardness of the former and its decreased damage to the polished Si wafer surface. It was feasible to realize ultra-precise polishing of the single crystal Si wafers making use of the polishing slurry doped with the nano-particulates, because in this case the cutting depth of the nano-sized abrasives was minimized, the removal of material was dominated by plastic flowage, and the polished surface quality and polishing efficiency could be assured.