▎ 摘　　要

We study the conductance spectrum of graphene quantum dots, both single- and multiple-dot cases. The single electron tunneling through a graphene dot is investigated and the periodicity, amplitude and line shape of the Coulomb blockade oscillations at low temperatures are obtained, which are consistent with the recent experimental observations. Further, we discuss the transport behavior when multiple dots are assembled in array and find a phase transition of conductance spectra from individual Coulomb blockade to collective Coulomb blockade.