Nanosized BaCe $O_3$ powders with the stoichiometric composition of a molecular level were synthesized by the citrate process based on the Pechini method. Polymeric precursor was formed by use of citric acid and ethylen glycol, as chelating agent of metal ions and reaction medium, respectively. Single phase orthorhombic structured BaCe $O_3$powders, about 100 nm sized and uniform shaped were obtained through the calcination of the polymeric precursor at 90$0^{circ}C$ for 4 h. Extremely small quantities of carbonate ionsCO/$_3$$^{2-}$ were completely decomposed at over 110$0^{circ}C$. The mean size of the powders was increased twice, however, it has very uniform distribution in its size and shape.