The adsorption properties of CO2 molecule on the LaCoO3 (1 1 0) surface with one/two O-2 pre-adsorption are studied by density functional theory method. Our calculated results show that the CO2 molecule acts as an acceptor when it is introduced into the LaCoO3 (1 1 0) surface with one O-2 pre-adsorption. It is inconsistent with the experimental results. It cannot explain the reason why the resistance of p-type perovskite oxide material increase after CO2 molecule is introduced. For the LaCoO3 (1 1 0) surface with two O-2 pre-adsorption, the role of CO2 molecule transforms to donor from acceptor. In this mode, the electrons of CO2 molecule transfer to the LaCoO3 (1 1 0) surface with two O-2 pre-adsorption, resulting in a decrease of hole-carrier concentration and an increase of resistance. The interaction between CO2 and the LaCoO3 (1 1 0) surface with two O-2 pre-adsorption is responsible for the CO2 sensing characteristics and mechanism of LaCoO3. (C) 2014 Elsevier B.V. All rights reserved.