An extensive grand canonical Monte Carlo simulation has been performed to study the adsorption behavior and the orientational, structure of CO2 confined in slit graphite pores, with a wide pore width range of 0.61 to 3.04 nm and pressures up to 3.41 MPa. The simulation results show that the minimum pore width for the adsorption of CO2 is 0.57 nm, the maximum adsorption occurs at pore width. H = 2.43 nm and pressure P = 2.56-3.41 MPa, and capillary condensation takes place only for H>2 nm. It is also found that the wall-perpendicular orientation becomes preferential with the increase of pressure.