Functionalized magnetic Fe_3O_4@SiO_2 composite nanoparticles were prepared by simply embedding iron oxide nanoparticles into MCM-41 through one-step synthesis process, followed by aminopropyls grafting on the mesopore channels, aiming to efficiently and conveniently uptake U(VI) from aqueous solution. The resultant material possesses highly ordered mesoporous structure with large surface area, uniform pore size, excellent thermal stability, quick magnetic response, and desirable acids resistance, confirmed by Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), N_2 adsorption/desorption experiments, powder X-ray diffraction(PXRD), and thermogravimetric analysis(TGA). Detailed U(VI) sorption test indicated that this material is indeed an effective U(VI) sorbent with fast sorption kinetics of less than 2 h, large sorption capacity of 160 mg/g at p H 5.0±0.1, and desirable selectivity towards U(VI) ions over a range of competing metal ions. The absorbed U(VI) can be easily desorbed by 0.01 mol/L or more concentrated HNO_3 solution, and the reclaimed sorbent can be reused with no obvious decrease of sorption capacity even after 4 sorption-desorption cycles. The present results suggest the vast opportunities of this kind of magnetic composite on the solid-phase extraction of U(VI). Functionalized magnetic Fe_3O_4 @ SiO_2 composite nanoparticles were prepared by simply embedding iron oxide nanoparticles into MCM-41 through one-step synthesis process, followed by aminopropyls grafting on the mesopore channels, aiming efficiently and conveniently uptake U (VI) from aqueous solution. The resultant material possesses highly ordered mesoporous structure with large surface area, uniform pore size, excellent thermal stability, quick magnetic response, and desirable acids resistance, confirmed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), N2 adsorption / desorption Experiments with powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). Detailed U (VI) sorption test indicated that this material is indeed an effective U (VI) sorbent with fast sorption kinetics of less than 2 h, large sorption capacity of 160 mg / g at p H 5.0 ± 0.1, and desirable selectivity towards U (VI) ions over a range of competing metal ions. The absorbed U (VI ) can be easily desorbed by 0.01 mol / L or more concentrated HNO3 solution, and the reclaimed sorbent can be reused with no obvious decrease of sorption capacity even after 4 sorption-desorption cycles. The present results suggest the vast opportunities of this kind of magnetic composite on the solid-phase extraction of U (VI).