The present study focuses on development of pure and Ru-doped TiO2 nanofibers as potential candidates for humidity sensing. Electrospun technique is used for fabrication of the nanofibers to evaluate their humidity sensing properties via QCM method. The obtained nanofibers are analyzed by X-ray diffraction and scanning electron microscopy techniques. The humidity adsorption kinetics and the mechanism of sensing humidity are explored, in details. The results of X-ray analyses reveal that TiO2 nanofibers with a mixture of anatase and rutile structures are successfully synthesized. Additionally, Ru reduces the crystalline size and intensity of the TiO2 peaks. The QCM results show that Ru-doping enriched the humidity sensing performance of TiO2 nanofibers. According to the DFT calculations, the introduction of Ru atoms into TiO2 leads to a sizable increase in the adsorption energy of the water molecule. It is also found that the Ru-doping makes an increase in the charge-transfer from the water molecule into the surface, which can result in an enhanced sensing response of TiO2 by decreasing the electrical resistance. The present study focuses on development of pure and Ru-doped TiO2 nanofibers as potential candidates for humidity sensing. Electrospun technique is used for fabrication of the nanofibers to evaluate their humidity sensing properties via QCM method. The obtained nanofibers are analyzed by X-ray diffraction and scanning electron microscopy techniques. The humidity adsorption kinetics and the mechanism of sensing humidity are explored, in details. The results of X-ray analyses reveal that T102 nanofibers with a mixture of anatase and rutile structures are successfully synthesized. Additionally, Ru reduces the crystalline size and intensity of the TiO2 peaks. The QCM results show that Ru-doping enriched the humidity sensing performance of TiO2 nanofibers. According to the DFT calculations, the introduction of Ru atoms into TiO2 leads to a sizable increase in the adsorption energy of the water molecule. It is also found that the Ru-doping makes an increase in the charge-transfer from the water molecule into the surface, which can result in an enhanced sensing response of TiO2 by decreasing the electrical resistance.