Abstract: A physical scheme design of a 10 MW accelerator-driven sub-critical gas-cooled fast reactor was studied. The coupling program COUPLE2.0 was applied, which couples MCNPX and ORIGEN. The physical parameters such as k_eff, proton efficiency, accelerator current, power peak factor and Doppler coefficient of 1 500 K varying with burnup time were obtained, and the safety feature of the system was analyzed. By further calculation the 350 d burnup of the system was obtained and the transmutation capability was analyzed. It is found that during the 350 d burnup, k_eff, accelerator current, power peak factor variations are relatively small. The system has good safety feature with deep sub-critical status in hypothetical accident. The total burnup is relatively shallow, but the system has good transmutation capability with the transmutation support ratio of 20.28.