The total conductivity of La0.9Ba0.1Ga0.8Mg0.2O2.85 (LBGM9182) and La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM9182) at 823-1273 K in air was about the same, and their hole conductivity measured by using an ion blocking method at 1073 K was also similar. The transference numbers of holes in both electrolytes at 1073 K in air were estimated at about 1%. The surface reaction rate constant of oxygen isotope on LBGM9182 is larger than that on LSGM9182 at 1073 K. The higher surface reactivity of LBGM9182 suggests that LBGM9182 is more sensitive to the existence of a small amount of H2O in the closed system of the oxygen isotope exchange equipment than LSGM9182. The single-SOFC cell tests were carried out at 973 K. The cell with LSGM9182 indicates better performance than that with LBGM9182 in single-cell tests at 973 K because the anode overvoltage of the latter is larger than that of the former. Furthermore, the anode overvoltage of the cell with LBGM9182 rapidly increased with operating time. The inferior cell performance with LBGM9182 is due to the increase of the ohmic resistance on the anode, which caused by the degradation of LBGM9182.