Abstract: The reduction backextraction behavior of Pu(Ⅳ) from 30%TBP/OK with EHEH was investigated under conditions of different temperatures, different concentration of EHEH and HNO3, various contactingtime and phase ratios respectively. It is shown that Pu(Ⅳ) from organic phase can be rapidly stripped into aqueous phase by EHEH; the batch stripping percentage of Pu(Ⅳ) approach 99% in contacting time of 5 seconds at phase ratio(o/a) 1∶1, compared with 89% in 30 seconds at phase ratio (o/a) 4∶1. It is also found that the higher reductant concentration, the lower acidity and the higher temperature could speed up the stripping extraction process of Pu. The application of EHEH to separate Pu from U in the 1 B contactor was studied by the 14stages counter current cascade experiment. It is shown that the recovery percentage of U reaches over 99.999% and the recovery percentage of Pu reaches over 99.99% at phase ratio (1BX∶1BF∶1BS)1∶4∶1. The separation factor of Pu from U(α(Pu/U))is 1.1×10⁴; the separation factor of U from Pu(α(U/Pu)) is 3.2×10⁵. The results show that EHEH as an orgnic reductant has obvious effect on the separation of Pu from U.