This article provides an overview of current research activities on the synthesis and applications of magneticnanocomposites, especially highlights their potential environmental remediations such as heavymetal (Cr, As, Pd, Hg) removal. After a brief introduction of the emergency situation of heavy metal pollutionall over the world and current techniques designed to deal with these situations, different syntheticmethods to fabricate various types of magnetic nanocomposites will be reviewed. The focus isto reveal the advantages of magnetic nanocomposites as an efficient adsorbent which is able to reducethe heavy metal concentrations well below the EPA requirement. At the same time, the conventional processcan be redesigned to be an economic and energetic one without using extra energy to recycle theadsorbent, which is desired for future. This review mainly deals with the heavy metal removal using magneticnanocomposites, the adsorption behaviors of heavy metal ions on the surface of novel adsorbentsare well investigated including the concentration effect of both contaminants and adsorbents, adsorptionkinetics, solution pH effect with regards to real application.