The plasmon excitation in ring graphene nanostructures is studied by time dependent density functional theory. In lower energy resonance region, compared with the same size graphene nanostructure, the main absorption peak of spectra of ring graphene nanostructures shows redshift. There are two main plasmon resonance modes, the low energy bonding mode and high energy anti bonding mode, in ring graphene nanostructures. Moreover, to a certain extent, the plasmon excitation in ring graphene nanostructures depends on the size of the system.
