Pure and Er-doped (0.5 at%, 1.0 at% and 2.0 at%) ZnO nanofibers are fabricated by electrospinning for high sensitivity detection of ethanol. We show that the diameter of the ZnO nanofibers decreases from 200 to 70 nm with the increase of Er content but the Er-doping significantly can improve the ethanol-sensing sensitivity of the ZnO nanofibers at an optimum operating temperature of 240 degrees C. At the optimal Er content of 1.0 at%, the sensitivity of the nanofibers is 3.7 times larger than that of pure ones, showing also a fast response (12 s) as well as a fast system recovering (3 s). Such an improvement of the sensing behavior can be attributed to the enhanced gas adsorption and fast reaction rate of Er-doped ZnO nanofibers. (C) 2015 Elsevier B.V. All rights reserved.