In this study, a bi-functionalized magnetic iron oxide composite which was covalently bound by ammonium and phosphonate groups has been employed as a novel sorbent for effective sorption of uranium (VI) from alkaline media. The maximum sorption capacity was observed at pH 9.0 with a capacity of 70.7 mg/g at CU(VI)initial = 21.7 mg/L. The sorption isotherm followed a pseudo-second order kinetic equation and could be described by a Freundlich isotherm. The thermodynamics research showed that the sorption was a feasible and endothermic process. Since the as-prepared material could be separated by magnetic field without filtration and centrifugation, it could be a promising sorbent for highly-efficient removal of U (VI) from alkaline solution.