Ba doped CeO2 nanopowders were prepared under mild temperature and pressure conditions by precipitation from metal nitrates with aqueous ammonium hydroxide. Spherical Ba doped CeO2 nanopowders were obtained with reaction at the temperature range of 210°C to 230°C for 6 h. The average size of the synthesized Ba doped CeO2 powders were below 10 nm and its distribution was narrow. The XRD pattern showed that the synthesized Ba doped CeO2 powders were crystalline with cubic phase of CeO2. This study has shown that the synthesis of Ba doped CeO2 nanopowders is possible under mild temperature and pressure conditions in ethylene gylcol solution. The effects of synthesis parameters, such as the solvent ratio of starting solution, pH of starting solution, reaction temperature and time, are discussed.