[en] New salt-free complexants for separating Pu(IV)from U(VI) in U-cycle of Purex process are investigated. Distribution experiment were carried out for Pu(IV), Pu(III) and U(VI) in the systems of extraction and back extraction. From these experiments, it is concluded that acetohydroxamic acid (AHA) complexes more readily with Pu(IV), and it can not only inhibit extraction of Pu(IV) in aqueous phase, but also preferentially strip Pu(IV) from 30 % TBP/OK into aqueous phase. By contrast, Pu(III) and U(VI) do not complex strongly with AHA