Abstract: By using n octanol and kerosene as diluent, the extraction behavior of Am(Ⅲ) and Eu(Ⅲ) from nitric acid solution is studied with N,N,N’,N’ tetrabutyl 3 oxa pentanediamide(TBOPDA),N,N,N’,N’ tetraisobutyl 3 oxa pentanediamide(T i BOPDA) and N,N,N’,N’ tetrabutyl 3,6 dioxa octanediamide(TBDOODA). The extraction equilibrium is an exothermic reaction and the extraction enthapy of americium is -80.54、-81.99 and-75.88 kJ/mol for TBOPDA,T i BOPDA and TBDOODA,respectively.It is found that the remarkable variation of HNO 3 concentration in equilibrium only slightly changes the shape and position of the visible absorption peak of the loaded organic phase. It implies that the variation of HNO 3 concentration does not affect the extraction mechanism. In IR spectrum the carboyl absorption peaks of both TBDOPDA and TBDOODA shift strongly to long wavelength after extracting HNO 3 or Eu(Ⅲ), at the same time the peak of carbon-oxgy-carbon has 6 cm -1 and 3 cm -1 shift for TBOPDA and TBDOODA, respectively.