This study was carried out to find the optimal operating conditions for separation of residual uranium from the simulated solution containing 19 elements. As an extractor, two miniature mixer-settlers with a total of 18 stages were used. Extraction yield of U, Np and Tc was about 99.2%, 32.1%, and 99.9%, respectively. The other elements were coextracted in the range of 1-4%. Extraction yield of U was exceed the results of previous study, which were caused the low extractability of U according to the coexisting elements. It was due to the characteristics of multi-stage extractor. Low extractability of Np was caused by various oxidation states. High extractability of Np may be attributed to the formation of complex with Zr and U. All elements extracted with TBP were stripped into aqueous phase more than 99% by 0.01 HNO₃. Fron the results, this process is not problem with respect to the removal of long-lived nuclides such as U, Np and Tc. To prevent the diffusion of radioactive nuclide, however, overall separation of Np in the same step was required, because Np was distributed in the raffinate and U product stream, respectively.