Abstract: In this paper, maleic anhydride, acrylonitrile and β-cyclodextrin modified by maleic anhydride were used as monomers. Terpolymer hydrogel β-cyclodextrin/maleic -anhydride-co-acrylonitrile-co-maleic anhydride(CD-AN-MAH) were synthesized, which was further oximated to get the amidoxime product(CD-AO-MAH). In order to explore the adsorption characteristics of both U(Ⅵ) and Th(Ⅳ) in appropriate conditions, several groups of adsorption experiments as the effects of pH, time and temperature were studied to learn the different adsorption behaviors of U(Ⅵ) and Th(Ⅳ). And the mechanism of the adsorptions were explored by the kinetics, isotherms and thermodynamics. It is found that the processes of U(Ⅵ) and Th(Ⅳ) adsorbed onto CD-AN-MAH and CD-AO-MAH are all fast adsorption kinetics conforming to the pseudo-second-order model. The adsorption effect of CD-AO-MAH for U(Ⅵ) is better than CD-AN-MAH under the same conditions. While for Th(Ⅳ) the adsorption effects of both CD-AN-MAH and CD-AO-MAH are not as good as U(Ⅵ). The results indicate that the amidoxime group has a promising selectivity for U(Ⅵ). The terpolymer hydrogel modified by amidoxime group can be used as a potential material for selective separation of U(Ⅵ) in solution system in the future.