Abstract: Electronic structure of multiwalled carbon nanotubes have been investigated as a function of the intershell coupling effect.The tight-binding model was employed.Theoretically，the intershell coupling makes energy bands of multiwalled carbon nanotubes split and the degeneracies in the energy bands reduced，and the bandgaps of multiwalled carbon nanotubes decreased.The small bandgaps of multiwalled carbon nanotubes ensure the presence of a vibrational manifold in the optical region for each shell so as to minimize optical emission.

Key words: multiwalled carbon nanotubes, coupling, electronic structure