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ZnO and TiO2 nanofibers are synthesized via electrospinning methods and characterized by x-ray diffraction,scanning electron microscopy,and transmission electron microscopy.Humidity sensors with double-layer sensing films are fabricated by spinning the ZnO and TiO2 nanofibers on ceramic substrates sequentially.Compared with sensors loading only one type of nanofiber,the double-layer sensors exhibit much better sensing properties.The corresponding impedance changes more than four orders of magnitude within the whole humidity range from 11%to 95%relative humidity,and the response and recovery times are about 11 and 7s,respectively.Maximum hysteresis is around 1.5%RH,and excellent stability is also observed after 180 days.The humidity sensing mechanism is discussed in terms of the sensor structure.The experimental results provide a possible route for the design and fabrication of high performance humidity sensors based on one-dimensional nanomaterials.