Combining experiments and first-principle calculations, mechanism of ozone detection on Cu2O(111) surface is proposed. Results show that O-3 is adsorbed without dissociation with E-ads = -2.89 eV and is completely dissociated in O-2 plus oxygen adsorbed with total enthalpy Delta H = -3.01 eV. These two reactions leads to a shift in the level Fermi of about 0.45 eV, which induces a p-doping. Thus the reaction of dissociation of O-3 on Cu2O(111) surface leads to a decrease in electrical resistance, as experimentally observed. (C) 2015 Elsevier B.V. All rights reserved.