Abstract: Computer code was presented to simulate the codecontamination (1A) of Purex solvent extraction process. The code can deal with four ingredients (UO²⁺₂, HNO₃, Pu⁴⁺, PuO²⁺₂) and the concentration profiles were modeled to evaluate the process condition of 1A. The experimental concentration profiles were fitted well with the calculated results. The simulated results show that the losses of Pu(Ⅵ) to the aqueous raffinate are one of important factors for total plutonium losses. When the feed solution is 3.0 mol/L HNO₃ solution containing 225 g/L uranium and 2.20 g/L Pu, the solvent stream is 30%TBP/kerosene, the scrub feed is 3.0 mol/L HNO₃ solution and the flow ratios of 1AF∶1AS∶1AX is 1.25∶0.75∶3.00, the percent of Pu(Ⅵ) (occupies total Pu) in 1AF should be less then 7% in order to reach over 99.9% plutonium recycled.