ORIGEN2.1 program was used to predict the cumulative amount of NP- 237 and Am-243 of minor actinides in spent fuel after a power of 1000 MW nuclear power units operating three year
and analysis the changes of the content of two nuclides that decayed short-term and long-term after the nuclear power units operating three year were analyzed. As to provide valuable references in the reprocessing of the spent fuel.