Abstract: In order to investigate the neutron economy and safety of Accelerator Driven System, IAEA launched the Co-ordinated Researched Program （CRP）, and issued an ADS benchmark. This ADS bench-mark was divided into several stages, and the 1^st stage devoted to analyzing the neutron performances of ADS and validating the nuclear databases and the codes. The burnup code system ANISN-DOT4.2-ORIGEN2 is developed. Initial enrichments of ²³³U which correspond to all given initial （BOL） k_eff values are calculated. and then, the spatial distributions of power density （BOL）, the void reactiv-ity effects, the spallation source effectiveness φ^*, and the evolution curves of k_eff and source as function of time are also calculated for every given k_eff （BOL）. The numerical results are in a good agreement with those of various countries.