In this work, magnetic nanoscale Fe3O4 particles were synthesized through coprecipitation of Fe(II) and Fe(III) in alkaline media. The structure, composition and properties of the nanoparticles prepared were characterized by transmission electron microscope (TEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). Catalytic efficiency of the Fe3O4 nanoparticles was tested in degradation of phenol solution. At pH 7, the chemical oxygen demand (COD) removal rate reached 70% in 3 hours. The heterogeneous catalyst exhibited efficient catalytic activity close to that of iron homogeneous catalyst but with less than 3% leaching of irons cation. Further, it performed well under much wider pH range (pH 3~7) compared to classic Fenton reagent, providing potential alternative as a novel heterogeneous Fenton catalyst for environmental remediation.