The Monte Carlo method of grand canonical ensemble is used to simulate the adsorption process of hydrogen storage in carbon nanotube. Results show that the hydrogen storage capacity of (30,30) armchair carbon nanotubes is 3.74 wt% at 77 K and 2 MPa and at 77 K 7.4 wt% and 10 MPa. H2 molecules are distributed mainly at the surface of carbon nanotube.