Abstract: The accelerator-driven sub-critical system has promising future in transmutation of nuclear spent fuels. A physical design of a 10 MW fast-thermal spectrum gas-cooled reactor was studied. The program COUPLE2.0, which couples with MCNPX and ORIGEN, was applied to compute this scheme, and the continuous energy neutron cross section was obtained by the nuclear data library of ENDF-7 which was modified with five different temperatures: 300, 600, 900, 1500, and 2500 K. The physical parameters such as k_eff, proton efficiency, delayed neutron fraction and accelerator current varying with the burnup time were obtained. The system during 350 d burnup was obtained and the transmutation capability was analyzed by the further calculation. It is found that during the 350 d burnup, the variations of k_eff and accelerator current are relatively small. The system has good transmutation capability with the transmutation support ratio of 24.86.