Novel single/multiwall hollow CeO2 microspheres were synthesized by self assemblage through hydrothermal method without any surfactant, the shells of which were consisted of CeO2 nanoparticles with mean size of 70nm. The influence of the molar ratio of urea to Ce(NO3)(3)center dot 6H(2)O on the morphology of the products was investigated and the formation mechanism of single/multiwall hollow CeO2 was proposed.