Grand canonical Monte Carlo method is used to simulate the adsorption of linear two-centre ethane molecules in MCM-41 of different pore sizes at different temperatures and a range of pressures.Beside the amount of adsorption, the local density profiles for the mass centre and methyl groups as well as the angle distributions simulated for the ethane molecules are used to explore microscopic and orientational structures of the adsorbate inside MCM-41. The results indicate that ethane molecules near the wall of MCM-41 prefer to lie on the surface both at 180 and 300 K, while the rest molecules exhibit a trend to be perpendicular to the wall,and the increase of temperature makes the molecules placed more randomly.In addition, the distributions show that the molecules in the vicinity of the centre are basically disordered even at a low temperature of 180 K.