Barium titanate (BaTiO₃) nanofiber was synthesized by electrospinning and by using the calcinations technique. Its morphologies were characterized by scanning electron microscopy, which showed that its average diameter was 80?C200 nm, and its length was over 0.1 mm. An impedance-type humidity sensor was then fabricated based on this BaTiO₃ nanofiber. It was unexpected to find that such sensor exhibited fast response and recovery, which were 5 and 4 s between 11% and 95% relative humidity, respectively. The long stability and humidity hysteresis properties of this sensor were also tested, and they were found to be optimum. These excellent sensing characteristics prove that BaTiO₃nanofiber is applicable for high-performance humidity sensors.