Thermodynamic assessment in the ternary systems ZrO2-CeO2-Y2O3 ,ZrO2-CeO2-Ce2O3 and the limiting binaries ZrO2-Y2O3,ZrO2-CeO2 ,CeO2-Y2O3, ZrO2-Ce2O3, CeO2-Ce2O3 as well as the modeling for oxides are reviewed comprehensively. Based on the recent estimations on the YO1.5 -CeO2, ZrO2 -CeO2 and ZrO2-YO1.5 systems, isothermal sections at 1 273 and 1 973 K of the ternary CeO2-ZrO2-YO1.5 system are calculated. In the system of ZrO2-CeO2-Ce2O3, the complex relation between the nonstoichiometry (y) in CeO2- y, the composition of the ZrO2-CeO2 solid solution and the oxygen partial pressure ( Po2 ) for different ZrO2 containing solid solutions Cez Zr1 - z O2 - x are evaluated from 1 473 to 1 773 K. The relation between the degree of Ce+ 4 reduction to Ce + 3 under different Po2 in the fluorite CeO2 - y and Cez Zr1- z O2 x solid solutions at different temperatures can be used as a guide in the development of functional ceramics.