Nanocrystalline CeO2 was prepared by hydrothermal crystallization method. XRD analysis indicates that the structure of the synthesized CeO2 is cubic with space group O5H FM3M. TEM photos reveals that nanocrystalline CeO2 is spherical in shape with a mean particle size of less than 100 nm. It was found that with increase of hydrothermal treatment temperatures the relative density of CeO2 nanocrystalline increased.