Abstract: A physical scheme design of pebble-bed reactor of accelerator-driven sub-critical system (ADS) was done to study the transmutation capability. The variation of effective multiplication factor k_eff and power with the burnup time was given by using the method of combination of MCNPX and ORIGEN. If the proton beam of accelerator is steady, the k_eff and power are nearly invariable by replacing the spherical fuel elements. The distribution of power density at different radial and axial distances and the transmutation of minor actinides (MA) were given. The result shows that the transmutation rate of Pu is higher and can reach 75%, the transmutation rate of MA is lower and only can reach 5%. But the transmutation effect of ²³⁷Np and ²⁴¹Am is much better, the transmutation rate of them can reach 59% and 89%, respectively.