Using the geometric configuration optimized from ab initio calculation, the energy band structure of CO adsorption on MgO(001) defective and irregular surfaces were studied by EHT crystal orbital method. The structures and components of the bands have been discussed. By means of analyzing the changes of bonding, CO binds at Mg(3c) cations considerably stronger than at regular Mg(5c) and Mg(4c) sites. The charge redistributions in the CO molecule and the substrate are considered. It is shown that CO may bind to the surface with a slight preperence for the O－Mg^2^+－C(CO) interaction. The oxygen vacancy of MgO(001) surface is more beneficial to CO adsorption and decompose on the surface than other configurations.

Key words: MAGNESIUM OXIDE, ADSORPTION, CARBON MONOXIDE, BAND, ELECTRONIC STRUCTURE, AB INITIO CALCULATION