Abstract: The effects of concentrations of C₂H₄NOH, H⁺, NO^-₃, Fe(Ⅲ) and temperature on the reaction rate of the Pu(Ⅳ)acetaldoxime were studied by spectrophotometry, and then the rate equation and the corresponding parameters were obtained.The reduction rate of Pu(Ⅳ) can be improved by either increasing the acetaldoxime concentration and the temperature, or decreasing the concentration of acid. However, the effects of concentrations of NO^-₃ and Fe³⁺ on the reduction rate of Pu(Ⅳ) are negligible.It is found that the rate constant is (39.51±0.05） (mol/L)^1.1·min^-1 at 25 ℃, and the activation energy is （88.96±9.43） kJ/mol. In the counter current cascade experiments with acetaldoxime used as reductant (in which 6 stages for supplemental extraction, 8 stages for stripping, and ratio of flow is 1BS∶1BF∶1BX＝1∶4∶1), the recoveries are more than 99.99% for U and 99.99% for Pu. The separation factor of Pu from U is 1.05×10⁴, while that of U from Pu is 2.7×10⁵.