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The synthesis of ultrafine cerium dioxide precursor via homogeneous precipitation was studied. Mixed aqueous solution of anhydrous cerium nitrate and urea was first heated to 85℃ for 2 h, and the prepared suspension was then aged at room temperature for various periods of time. White precipitate was finally collected by centrifuging and washed with distilled water and anhydrous ethanol. The obtained cerium dioxide (CeO2) precursor was observed with SEM. It was found that the morphology and size of the precursor were strongly affected by aging time and stirring conditions (with or without stirring).The precipitated fine spherical particles of the precursor changed their shape from ellipse to slice or directly to slice. Fine spherical monodispersed (300 nm) precursor powders could be obtained by controlling the aging time. Stirring the solution also could change the reaction process and thus the morphology and size of the precursor were changed.