A mixed potential type yttria-stabilized zirconia (YSZ)-based NO2sensor attached with NiO sensing electrode (SE) with efficient three-phase boundary (TPB) processed by electrospinning technology was fabricated. The effect of the structure and area of TPB on the gas sensing performance of the sensor was investigated systematically. The YSZ nanofiber array was directly deposited on YSZ substrate by electrospinning method to construct efficient three-dimensional TPB. The sensor (S30) based on YSZ substrate processed by electrospinning method with the flow rate of 1.5 mL/h for 15 min and NiO-SE exhibited the highest sensitivity (77.4 mV/decade) to 5–500 ppm NO2at 510◦C, which was 2.6 times as the sensor (S00) with unprocessed YSZ substrate. The response value of S30 to 100 ppm NO2could reach 109 mV at 510◦C, which increased about 51 mV comparing with S00. Moreover, the sensor (S30) also displays fast response and recovery rates, good repeatability, excellent selectivity, moisture resistance and long-term stability. The elevated NO2sensing performance of the sensor is attributed to more active sites of electrochemical reactions by increased area of three-dimensional TPB.