Electrical properties of Y 2 O 3 -doped CeO 2 -rich ZrO 2 -CeO 2 system were characterized with a view point of its point-defect structural scheme. Theoretical calculation of partial electronic and ionic conductivity from total conductivity was done to investigate the combined homovalent and aliovalent doping effect on the overall electrolytic property. According to our study, combined homovalent and aliovalent doping can be one of the key solutions to overcome the fatal disadvantage of limited electrolytic stability of doped ceria system by which properly enhances the ionic conductivity and suppresses the electronic conductivity all at once. Feasibility and limitation of Y 2 O 3 -doped CeO 2 -rich ZrO 2 -CeO 2 system as a potential alternative electrolyte material for low or intermediate temperature SOFC were discussed.