The electrical conductivity of CeO2-ZrO2 system was measured as functions of the temperature and oxygen partial pressure and of the composition. The ionic conduction was prevailing in the ZrO2 rich phase due to the increase of ionic defect concentration via homovalent doping effect. The enhancement of n-type electronic conductivity was observed in intermediate and CeO2 rich phase compared with pure CeO2, which originated either from homovalent doping effect or increase of electronic mobility due to the change of transport mechanism.