Abstract: The extraction of Pu(Ⅳ) and separation of Am(Ⅲ) from Pu(Ⅳ) by dihexyl N, N-diethyl cabamyl methylene phosphonate (DHDECMP) -diethyl benzene (DEB) in nitric acid medium is described.The distribution ratio (D) of Pu(Ⅳ) is studied as a function of a number of parameters such as concentration of nitric acid, concentration of extractant, contact time and temperature.Experimental results show that the distribution ratio of Pu(Ⅳ) decreases with increase of temperature and increases with concentration of nitric acid and DHDECMP. The enthalpy change △HPu is estimated to be -33 kJ/mol. The logarithmic plots of DPu-DHDECMP is a straight line with a slope of 1.9. The separation factor for Am from Pu is more than 50. This method can be used to separate Am from Pu(Ⅳ).