Abstract: A mixed-potential NH₃ sensor based on an 8 mol% yttria-stabilized zirconia (8YSZ) plate and a WO₃ electrode (8YSZ-WO₃ sensor) was fabricated and studied. The effects of electrode calcination temperature on the performance of the sensor were investigated. The microstructures of the electrode and the change of the sensor performance were investigated at calcination temperatures of 600, 650, 700 and 750 ℃ respetively. And the working mechanism of the sensor was analyzed. It was found that the sensor had the best performance when the calcination temperature was 700 ℃, and the response value of the sensor to 250×10^-6 NH₃ was 59.35 mV at 550 ℃ and the sensitivity was 52.65 mV/decade. Furthermore, the sensor was identified to be consistent with the mixed-potential model.