Abstract: By using n octanol and kerosen as diluent, the extraction behavior of technetium from nitric acid solution is studied with N,N,N'N' tetrabutyl 3 oxa pentanediamide(TBOPDA),N,N,N'N' tetraisobutyl 3 oxa pentanediamide(TiBOPDA) and N,N,N'N' tetrabutyl 3,6 dioxa octanediamide(TBDOODA). The extraction equilibrium is an exothermic reaction. The composition of the extraction complex and the extraction mechanism are also examined. The extraction reaction is H ++TcO - 4+ i SHTcO 4· i S(S is extractant). When the concentration of nitric acid is 0.5,2.0 and 4.0 mol/L, i equals 2, 1 5 and 1 0, respectively for both TBOPDA and TiBOPDA; whereas i equals 1.0 for TBDOODA in above three nitric acid solutions. At 25 ℃ and c (HNO 3)=2 0 mol/L, the apparent extraction constant K ex is 18 5, 19 2 and 4 9 for TBOPDA (0 1 mol/L), TiBOPDA(0 2 mol/L) and TBDOODA (0 1 mol/L), respectively. The change of thermodynamic functions of extraction reaction, Δ H, Δ S and Δ G are measured or calculated.