Abstract: A two-layer Zr_0.8Sc_0.2O_1.9/Ce_0.9Gd_0.1O_1.95 heterostructure has been modeled by the molecular dynamics method in a box containing about 27 thousand atoms. It is shown that this system retains on the whole the crystallographic characteristics of layers doped with zirconia and ceria, having a fluorite structure. Crystal structure distortions are observed in a narrow boundary layer with a thickness of few angstrom. An analysis of pair correlation functions indicates that the oxygen sublattice in the heterostructure is disordered. The calculated values of the layer-by-layer diffusion coefficient of oxygen and the diffusion activation energy are compared with the data of both direct physical and computer experiments.