Environmental pollution such as hexavalent chromium has been extremely released into the environment and significantly increased global concern. Hexavalent chromium has carcinogen and mutagen effect on organisms. In this study magnetite (Fe3O4) nanoparticles were successfully synthesized by sol-gel method with the purpose of removing Cr(VI) from waste water. The phase structures, morphologies, particle sizes, chemical composition, and magnetic properties of magnetite nanoparticles have been characterized by X-ray diffraction, scanning electron microscopy, energy –dispersive analysis by X-ray spectrometer and vibrating sample magnetometer. Synthesized magnetite nanoparticles demonstrated high capacity of hexavalent chromium adsorption. The maximum adsorption of Cr(VI) by Fe3O4 nanoparticles occurred at pH 8.2. The adsorption efficiency of Cr(VI) was explained in terms of Freundlich and langmuire equations.