Abstract: The nanocrystalline ceria-based precursor powder doped with samarium (Sm), gadolinium (Gd) and both of them were prepared separately via a homogeneous precipitation process where the urea and hexamethylenetetramine (HMT) as precipitants with the high-purity reagents Ce(NO3)3·6H2O, Sm2O3 and Gd2O3 as starting materials were both calcined at 700°C for 4.5 hr. Characterizing the phase, morphology, particle size and specific surface area of the products with XRD, SEM and Brunauer-Emmett-Teller (BET), the results showed that both the synthesized powder can be controlled efficiently via controlling the reaction conditions. When the total ion concentration of mixed metal is 0.04 mol/L and the initial concentration of precipitants is 0.5 mol/L with a pH value 6.8, the product from calcined precursor powder presents a single cubic fluorite-type structure with high phase purity and crystallinity, and the size distribution shows that the sphere-like nanopowder particles are in the range from 21 to 28 nm. The synthesized process proposed can yet be regarded as a new reliable approach to preparing the ceria-based electrolytic materials with more homogeneous finer particle size and higher activity at low temperature.