Adsorption mechanism of coal seam and carbon monoxide gas is studied in microscopic view by using first-principles calculation methods based on quantum mechanics. Due to complexity of coal structure, graphite is used to take place of coal seam for simulation. A model of adsorption of carbon monoxide on graphite is established. Three typical sites with high symmetry on graphite surface are considered. They are top, bridge, and hollow adsorption sites. It shows that bridge site has the highest adsorption energy as carbon monoxide molecule is perpendicular to graphite(001) surface with carbon atom near graphite film.