Herein, the ethylenediamine modified magnetic graphene oxide (Fe3O4/GO-NH2) materials were used to eliminate Hg(II) and methylene blue (MB) dye from single aqueous solutions. The various adsorption conditions of Fe3O4/GO-NH2 materials were explored and the experimental process highly depended on the initial pH, contact times and initial concentrations of Hg(II) and MB. The Langmuir and Freundlich isotherm models were employed to explore the adsorption behaviours and the kinetics experimental process were described by the pseudo-first-order and pseudo-second-order model. The experiments show that adsorption amounts of Fe3O4/GO-NH2 materials for Hg(II) and MB reached 147.68 mg·g−1 and 236.97 mg·g−1, respectively. The adsorption process was well correlated with pseudo-second-order kinetic model and the Langmuir isotherm model, which indicates the removal processes of Fe3O4/GO-NH2 nanocomposites for Hg(II) and MB were monolayer chemisorption.