A mixed-potential type NO₂sensor based on stabilized-zirconia (YSZ) solid electrolyte and novel trirutile CoTa₂O₆sensing electrode (SE) prepared through the sol-gel method was developed at high temperature. The effect of CoTa₂O₆sensing electrode material calcinated at different temperatures on NO2 sensing property was mainly investigated and the device attached with CoTa₂O₆-SE sintered at 1000℃ gave the highest response of 93 mV to 100 ppm NO₂and fast response and recovery times at 650 ℃. The response of the sensor utilizing CoTa₂O₆-SE annealed at 1000 ℃ displayed segmentally linear relationship to the logarithm of NO₂concentration in the ranges of 0.5-5 ppm and 5-500 ppm, which the sensitivities were 12 and 80 mV/decade, respectively. Meanwhile, the present fabricated device also showed good reproducibility, selectivity, long-term stability and slight effect of oxygen and moisture at 650 ℃. Furthermore, the mixed potential sensing mechanism proposed was discussed quantitatively and further verified by polarization curve measurement.