LnFeO(3) (Ln = Sm, Nd, La) nanofibers are synthesized via electrospinning and the humidity sensors based on LnFeO(3) nanofibers are fabricated and measured at different relative humidity to investigate the humidity sensing properties. The optimal working frequency of LnFeO(3) nanofibers humidity sensors are all 100 Hz at which the sensors are of good linearity and high response. Compared with other LnFeO(3) nanofibers humidity sensors, SmFeO3 nanofibers humidity sensor shows the best sensitivity and the impedance variation is more than five orders of magnitude with the relative humidity changing from 11% to 95%. The response time is about 10 s and the impedance versus RH curve is of good linearity. (The linear correlation coefficient is 0.98.) The results indicate that the SmFeO3 nanofibers with low Ln-Obinding energy exhibit the best humidity sensing properties compared with others. We expect that our work has a great significance for fabricating high-performance humidity sensors.