A novel magnetic nanocomposite was synthesized using graphene oxide (GO), polyethylenimine (PEI), and Fe3O4 to removal hexavalent chromium (Cr(VI)) from water and soil. Therein, GO was functionalized with plenty of -NH2 by the modification of PEI through an amidation reaction, and the resulting GO/PEI reacted with FeSO4 center dot 7H(2)O and NaBH4 to obtain RGO/PEI/Fe3O4 (the optimal one is designated as ORPF) through an oxidation- reduction reaction. ORPF could effectively adsorb Cr(VI) through electrostatic attraction, and the adsorbed Cr(VI) ions were partially reduced to trivalent chromium (Cr(III)) with low toxicity by RGO (pi electron). Afterward, the resulting ORPF-Cr could be conveniently removed from water with a magnet, achieving the maximum Cr(VI) removal capacity of 266.6 mg/g. Importantly, ORPF, once carried by sponge particles, could efficiently remove Cr(VI) from soil, and the resulting mixture could be facilely collected with a magnet on a filter net. Besides, the leaching experiment suggested that, when supported by filter paper, ORPF was able to decrease the number of leached Cr(VI) ions and meanwhile reduce them to Cr(III). This work provides a promising approach to remediate Cr(VI))-contaminated water and soil using a nanocomposite, Which has a huge number of application prospects.