The invention provides a pattern-reconfigurable antenna based on a graphene composite structure frequency selective surface to solve the problem that the gain and beam bandwidth of an antenna cannot be changed flexibly in the prior art. The pattern-reconfigurable antenna comprises a rectangular waveguide feeder, a rectangular radiation element, a baffle board, a frequency selective surface, and a direct-current bias voltage Vc. The frequency selective surface includes a graphene composite structure, a dielectric substrate, and a square patch array or graphene composite structure, which are stacked from top to bottom. The graphene composite structure is composed of a graphene layer, an alumina layer and a polycrystalline silicon layer which are stacked sequentially. The direct-current bias voltage Vc is applied between the graphene layer and the polycrystalline silicon layer. The rectangular radiation element is arranged on the baffle board, the frequency selective surface is fixed above the baffle board through four support columns, and the rectangular waveguide feeder is fixed below the baffle board. The radiation gain and beam bandwidth of the antenna can be changed flexibly, and reconfigurable pattern of a millimeter wave antenna is realized.