▎ 摘　　要

We observed the Shubnikov-de Haas and the Aharonov Bohm oscillations in a graphene nanoring structure of 1 mu m in diameter and with a 125 nm channel width. We found a separation of 2 Delta V-g=17.5 V between electron and hole Landau levels in the plot of longitudinal resistance as a function of gate voltage and magnetic field. This separation can be understood as a result of the transport gap, Delta V-t=20 V, in the density of state. The Aharonov Bohm effect was observed in magnetoconductance with poor visibility because of the short phase coherence length of the graphene nanoring structure.