The effect of low energy Ar ion bombardment on the structure and field emission properties of CuO nanowires was studied. The morphology and structure were characterized by scanning electron microscopy and high resolution transmission electron microscopy. Non-crystallization of the nanowire was found after bombardment, which was due to the diffusion of the defects induced by knock-on ions. The work function of nanowires decreased after bombardment which was attributed to the preferential sputtering of oxygen. Field emission measurements showed that after bombardment with different energy the turn-on field decreased first and then increased with increasing ion energy. The lowest turn-on field was obtained with the optimal ion energy of 215 eV. The typical turn-on fields of the as-grown samples and samples after Ar ion bombardment with energy of 215 eV were about 6.5 V/mu m and 5.25 V/mu m, respectively. The lowered field emission turn-on field was attributed to the increase of field enhancement factor and decrease of work function. (C) 2014 Elsevier B.V. All rights reserved.