Environmental pollution is a serious issue for human being. In the present study, we propose a C-Fe3O4 composite magnetic nanoparticles for the adsorption of dye pollutants. Since carbon shows high affinity for dye molecules and Fe3O4 shows benign response to a magnet, the material is suitable for remediation of environmental pollution in a convenient way. The material was prepared and was characterized by scanning electron microscopy, nitrogen sorption and powder X-ray diffraction. As a model dye, methyl red was used to evaluate the adsorption performance of the nanocomposite. The result demonstrates that the composite material can adsorb methyl red efficiently and it can be easily recovered by an external magnet, which simply the operational process in comparison with traditional centrifugation or filtration. It is a promising material for environmental remediation.