Abstract: In this paper, results are reported on the extraction behaviors of uranium (IV)by 31 kinds of crown ethers with various substituting groups from hydrochloricacid solutions. Results indicate that DCH's (dicyclohexl-crown ethers) in 1,2-dichloroethane provide best extraction of uranium (IV). The effects of the concen-trations of DCH, U (IV) and HCl in both phases on the extraction are alsostudied. It is found that U (IV) is not extracted in 5.0 M HCl by DCH, but thedistribution coefficients of U (IV) increase rapidly when HCl concentration isincreased to 8.0--8.5M. Using the slope method and the method of isomolarseries, the extracted species are identified as H_2UCl_6·2DCH. The extraction capaci-ties of five DCH's for uranium decrease in the order: DCH--27C_9, DCH--24C8,DCH--18C6, DCH--30C10, DCH--21C7. Experimental results indicate that theextraction reaction is as follows: U~(4+)+2H~++6Cl~-+2DCH=H_2UCl_6.2DCH