Abstract: The electrolytic oxidation of hydrazine, U(Ⅳ) and Pu( Ⅲ) has been studied in HNO3 medium using controlled potential technique. The anode is made of platinized tantanium. The results obtained indicate that the overpotential of oxygen evolution in nitric acid solution is lower by about 200. mV than that in perchloric acid solution. The hydrazine and pu( Ⅲ) are oxidized readily. Besides, the oxidation rate for hydrazine increases with flow velocity and decreases with increase in HNO3 concentration apparently, whereas the oxidation of Pu(IV) and U(Ⅳ) requires a large overpotential. By the electrolysis of 43 ml of the synthetical "1BP" solution containing 0.011M Pu(Ⅲ)-0.0015 M U(Ⅳ)-0.133M N2H5+-1.71M HNO3 at a potential of 900-1300 mV vs SCE for 60 minuts, the oxidation of hydrazine, U(Ⅳ) and Pu(Ⅲ) in the solution is almost complete.