In this paper, the mechanical properties and oxygen self-diffusion in partially reduced CeO2 have been investigated by using molecular dynamics simulations at various levels of non-stoichiometry and temperatures. Under a reducing environment, pure ceria experiences significant chemical volumetric expansion, which is described by coefficient of compositional expansion (CCE). It is found that CCE is about 0.084 and varies within 2% over the whole range of temperature. Meanwhile, elastic stiffness tensor of the non-stoichiometric structures remains cubic The Young's modulus decreases with increasing vacancy concentration, while the variation of the Poisson's ratio is found to be negligible. The oxygen diffusivity is computed by mean square displacements which increase initially but descend with increasing non-stoichiometry. In addition, the oxygen migration energy is extrapolated to be 0.4 eV which is consistent with reported experiment data. (C) 2012 Elsevier B.V. All rights reserved.