A magnetic Fe3S4-C composite adsorbent with micro/nanostructure was fabricated by a facile one-step solvothermal method using glucose as carbon source. The prepared products are of a tremella-like micro/nanostructure with magnetic properties and a surface area of 12 m2 g-1. The carbonaceous materials disperse uniformly on the surface of the tremella-like composites. Further experiments have revealed that glucose plays an important role in formation of such structured composites. It not only determines the morphology but also supplies functional groups which act as active sites in the adsorption process. More importantly, the composites can remove contaminants in water with high efficiency and be separated quickly at a low external magnetic field, and can be regenerated after washing with ethanol, showing good recycling performance. This work not only gives a deep insight in to the formation of novel micro/nanostructured magnetic composites but also supplies a new efficient adsorbent for water treatment.