Abstract: The mesoscopic transport through a quantum dot and a toroidal carbon nanotube (TCN) coupled system is investigated with the nonequilibrium Green's function technique.The coherent tunneling is strongly related to the energy structures of the TCN and the quantum dot.The Aharonov-Bohm effect causes energy levels of the TCN to change periodically,and the tunneling current oscillates with the magnetic flux.The detailed nanostructure of TCN exhibits metal-semiconductor transition,and this behavior is reflected in the output current.The matching-mismatching of quantum levels of the sub-systems plays important role in the mesoscopic transport.

Key words: mesoscopic transport, carbon nanotube, quantum dot