A high performance mixed potential type gas sensor based on stabilized zirconia (YSZ) and NiNb₂O₆as sensing electrode was fabricated and used for detection of acetone at 650℃. NiNb₂O₆prepared via a facile sol-gel method and sintered at different temperatures was characterized using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The present study mainly focused on the effect of sintering temperature (800℃, 1000℃, 1200℃) of NiNb₂O₆-SE materials on acetone sensing characteristics at 650℃. Results indicated that the sensor using NiNb₂O₆-SE sintered at 1000℃exhibited the largest sensitivity to acetone in the concentration range of 5-500 ppm at 650℃, which the slope was-79 mV/decade. The response for the sensor attached with a NiNb₂O₆-SE sintered at 1000℃to 100 ppm of acetone was approximately -113 mV. Moreover, the present sensor could detect even 500 ppb acetone with an acceptable response. The present device also displayed fast response and recovery times, good repeatability, slight sensitive effect to humidity, small drifts in 40 days measured periods, and acceptable selectivity at 650℃. Additionally, the mixed potential mechanism was further demonstrated by polarization curve.