Abstract: Satisfactory results were obtained for the extraction of tetra-and hexavalent uranium from hydrochloric acid solutions by dibenzo-18-crown-6-nitrobenzene.In order to elucidate the extraction mechanism of uranium with crown ether, the characteristics of uranium entering into organic phase and the composition of solid complexes extracted were studied. The results indicate that tetra-and hexavalent uranium are extracted from hydrochloric acid by dibenzo-18-crown-6 as complex anionic species: (UC16)2 and (UO2C14)2- respectively. Using the saturated extraction method and the method of isomolar series, the species extracted were identified as H2UC16·2DBC and H2UO2C14·2DBC respectively. The effects of alkali metal on the extraction of uranium are in accord with the sequence of the complexation between the cations and crown ether: K+>Na+>Li+. When a small amount of potassium is added to hydrochloric acid, the extraction of uranium could be greatly increased.