Coprecipitation with carbonates is an effective method for synthesis of the doped ceria nanopowder. This study compared the compositions and properties of the Gd2O3-doped CeO2 (GDC) nanopowders resulted by two ammonium carbonates, including a carbonate mixture from China and a pure carbonate reagent from abroad. It was found that the precursors from the two precipitants were same to each other in composition, with a formula (NH4)0.25CeGd0.25(CO3)2·2H2O. However, the GDC nanopowder resulted by the carbonate mixture had smaller particle sizes and thus better sinterability than that resulted by the pure ammonium carbonate reagent.