Abstract: The effect of phase-contact time, water phase acidity, concentration of extractant and the presence of some impurity on the extraction of Pu (Ⅳ) and Am (Ⅲ) by 1-phenyl-3-methyl-4-benzoylpyrazolone-5 (PMBP) in organic solution from nitric acid solution has been studied. The efficiency of Pu stripping with H2C2O4 solution was determined and optimum conditions of Pu and Am separation were found. A simple and effective radio-chemical method was presented for the determination of small amount Pu in Am, and was successfully used for the detection of Pu in the technological process of the separation of transplutonium elements from reactor-irradiated target. The yield of Pu by this method is (98±3)% for extraction and (96±2)% for stripping, and a decontamination factor of~ 105 from Am can be obtained.