Abstract: Kinetic study of Np(Ⅵ) reduction by tert butyl hydrazine in nitric acid media is performed by spectrophotometry. The effects such as concentration of TBH,H +,NO 3 -,UO 2 2+ ,Fe 3+ and temperature are investigated. The results show that the reaction rate equation may be expressed as follows: d c (Np(Ⅵ))/d t = kc (Np(Ⅵ)) c 0.9 (TBH)/ c 0.75 (H +). The rate constant of the reaction at 25 ℃ equals to 5.44 (mol/L) -0.15 ·min -1 . The activation energy of the reaction equals to 61.2 kJ/mol.The influences of NO 3 -,UO 2 2+ ,Fe 3+ on the reaction rate are negligible in the concentration range studied. The reaction rate increases apparently with rising temperature.