Abstract: The reduction stripping behavior of Pu(Ⅳ) from 30%TBP/OK with HSC was investigated under conditions of different temperatures, different concentration of HSC, concentration of HNO₃, concentration of NO₃^-, concentration of U in organic phase, various contacting-time, phase ratios, respectively. The results show that the longer phase contacting-time is, the higher reduction concentration is, the higher U concentration in organic phase is, the higher temperature is, and the lower HNO₃ concentration and the NO₃^- concentration are, the higher stripping rate of Pu is. The application of HSC to separate Pu from U in the 1B contactor was studied by the 16 stages counter current experiment (in which 6 stages for supplemental extraction, 10 stages for stripping). It is shown that the recovery percentage of U reaches over 99.99% and the recovery percentage of Pu over 99.99% at phase ratio 1BF∶1BX∶1BS＝4∶1∶1. The separation factor of Pu from U (SF_Pu/U) is 2.8×10⁴, and the separation factor of U from Pu (SF_U/Pu) is 5.9×10⁴. The results show that HSC as a new organic reductant can effectively achieve the separation of Pu from U.