Abstract: Lattice constant of oxide is amajor factor for synthesis and applicat ion of materials.Usually, theoretic simulation is one of a customary method for the materials research. An equation is given for calculating the correlation between the composition lattice constant of nanosize CeO₂ system solid solution powders. The computational results are corresponding to the experimental data by wet chemical synthesis.The error rate is not bigger than 0. 7% , 1. 7%, 3. 4% , 0.4% for CeO₂- ZrO₂, CeO₂- Bi₂O₃, CeO₂- La₂O₃, CeO₂- ZrO₂- ThO₂ system respect ively.

Key words: lattice constant, nanosize CeO₂ system solid solution powders, theoretical study