Polyamidoxime groups functionalized magnetic adsorbent was prepared by sequential grafting of SiO2, poly(glycidylmethacrylate) p(GMA), and diaminomelanonitrile (DAMN) on the Fe3O4 nanoparticles (MP). Firstly, the MP was synthesized by thermal co-precipitation reaction and then grafted with 3-aminopropyltriethoxysilane (APTES) to obtain amine group ended silica layer (i.e., MP/SiO2-NH2). For grafting of star type fibril polymer, atom transfer radical polymerization (ATRP) initiator was attached on the MP/SiO2-NH2 to obtain Br-ended MP/SiO2-NH-Br. Then, DAMN ligand was immobilized on the MP/SiO2/p(GMA) via epoxy ring opening reaction. The nitrile group of the DAMN ligand was converted in to amidoxime group (AO) by the reaction with hydroxylamine. The MP/SiO2/p(GMA)-AO nanoparticles were characterized by analytical methods, ATR-FTIR, SEM, X-ray diffraction (XRD), differential thermal analysis (DTA), and BET surface area analyzer. The maximum adsorption capacities as prepared adsorbents (i.e., MP, MP/SiO2-NH2, MP/SiO2/p(GMA)-OH, MP/SiO2/p(GMA)-DAMN and MP/SiO2/p(GMA)-AO for U(VI) ions were determined. The maximum adsorption pH was 6.0 for MP/SiO2/p(GMA)-AO, and the maximum amount adsorbed U(VI) ions was 760.3 mg g(-1). The equilibrium time was 30 min, and the experimental data was described with the Langmuir and Temkin models. The second-order kinetic best fitted the experimental data. The MP/SiO2/p(GMA)-AO showed good reusability for ten cycles of adsorption-desorption with negligible changes in the adsorption performance and stability. The selectivity of the MP/SiO2/p(GMA)-AO was also tested using artificial water after spiking with various amount of U(VI) ions. The experimental result indicated that MP/SiO2/p(GMA)-AO has high selectivity for U(VI) ions in the presence of other metals. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.