Aligned porous SnO2 nanofibers are obtained by electrospinning with the collector of parallel wedge-shaped electrodes and then by oxygen plasma treatment and annealing. The morphology and crystal structure of the fibers are analyzed by scanning electron microscopy and x-ray diffraction, and the effects of the morphology and alignment on ethanol sensing properties of the fibers are investigated. The results show that the porous SnO2 fibers with an average diameter of tens of nanometers can be deposited orderly on the micro-hotplate with the auxiliary electrodes. The aligned porous fibers exhibit higher sensitivity and faster response compared with randomly oriented ones at the operating temperature of 300 degrees C.