After adding 8Y-ZrO2 powders to 3Y-ZrO2 powders at ratios of 0, 33, 50, 67, and 100% by weight, the mixed yttria-stabilized zirconia specimens were fabricated into thin plate using tape~casting method and then sintered at 150$0^{circ}C$ for 4h in air. The crystalline structure, microstructure and electrical properties of the sintered zirconia thin plates were investigated by using X-ray diffractometer, scanning electron microscope and impedance analyser, respectively. At the temperatures higher than 75$0^{circ}C$, the sintered thin plate with 33% 8Y-ZrO2 content shows higher mechanical properties and lower electrical resistivity than 8Y-ZrO2 thin plate which is generally used as an electrolyte for solid oxide fuel cells. This is due to the fact that the zirconia thin plates with low 8Y-ZrO2 content maintain the slope of low temperature region up to high temperatures, whereas at temperatures higher than 50$0^{circ}C$ the slope decrease in the zirconia thin plates with high 8Y-ZrO2 content.