Abstract: This work concerns the nuclide transformation in the sub critical reactor of accelerator driven system(ADS), the results indicate the ADS has probability to sufficiently use nuclear resource. The best neutron flux rate is φ ≈10 14 cm -2 ·s -1 for thermal sub critical system and φ ≈10 15 ～10 16 cm -2 ·s -1 for the fast one. Under the same inventory, the number of fissile nuclei in saturation condition for the fast system is larger than those for the thermal one.