Abstract: On the base of the preparation and stabilization of Np(Ⅳ),Np(Ⅴ) and Np(Ⅵ), the distributions of them between dilute TBP/kerosene and aqueous phase are studied. The influences of the concentrations of nitric acid, aluminum nitrate and uranyl on the extraction of Np(Ⅳ,Ⅴ,Ⅵ) by 5 % TBP/kerosene are investigated at temperature of 25 ℃. The equations of extraction reactions at corresponding conditions are obtained. The influences of the concentration of TBP on the extraction of Np(Ⅳ,Ⅴ,Ⅵ) are studied, The extraction reaction equations of them and the corresponding apparent equilibrium constants at temperature of 25 ℃ are as follows: Np 4+ +4NO - 3+2TBPNp(NO 3) 4·2TBP, K ex (Np(Ⅳ))=0.705 mol -6 ·L 6;NpO + 2+ NO - 3+ TBPNpO 2NO 3·TBP, K ex (Np(Ⅴ))=0.0 378 mol -2 ·L 2;NpO 2+ 2+2NO - 3+TBP NpO 2(NO 3) 2 ·TBP, K ex (Np(Ⅵ))=2.15 mol -3 ·L 3, respectively. From 25 ℃ to 50 ℃, the enthalpy changes of the extraction reactions are as follows: Δ H (Np(Ⅳ)) =1.18 kJ/mol, Δ H (Np(Ⅴ)) =-3.71 kJ/mol and Δ H (Np(Ⅵ)) =-2.78 kJ/mol。