Graphene oxide/Fe(3)O(4) (GO/Fe(3)O(4)) composites were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The removal of Cu(II) and a natural organic macromolecule (fulvic acid (FA)) by GO/Fe(3)O(4) was investigated. The mutual effects of FA/Cu(II) on Cu(II) and FA sorption onto GO/Fe(3)O(4), as well as the effect of pH, ionic strength, FA/Cu(II) concentrations, and the addition sequences of FA/Cu(II) were examined. The results indicated that Cu(II) sorption on GO/Fe(3)O(4) were strongly dependent on pH and independent of ionic strength, indicating that the sorption was mainly dominated by inner-sphere surface complexation rather than outer-sphere surface complexation or ion exchange. The presence of FA leads to a strong increase in Cu(II) sorption at low pH and a decrease at high pH, whereas the presence of Cu(II) led to an increase in FA sorption. The adsorbed FA contributes to the modification of sorbent surface properties and partial complexation of Cu(II) with FA adsorbed. Different effects of FA/Cu(II) concentrations and addition sequences on Cu(II) and FA sorption were observed, indicating the difference in sorption mechanisms. After GO/Fe(3)O(4) adsorbed FA, the sorption capacity for Cu(II) was enhanced at pH 5.3, and the sorption capacity for FA was also enhanced after Cu(II) sorption on GO/Fe(3)O(4). These results are important for estimating and optimizing the removal of metal ions and organic substances by GO/Fe(3)O(4) composites.