Abstract: Fe3O4 nanoparticle was prepared by the micro-wave hydrothermal method in the paper. The influences of different factors on the average diameter of Fe3O4 nanoparticle were evaluated by the orthogonal-design method to obtain the optimum parameters for preparing the nanoparticle. Four factors with three levels were considered in the experiment，which were molar proportion of [Fe3+]/[Fe2+]，crystallization temperature，crystallization time and pH. The surface of the Fe3O4 magnetic nanoparticle was modified by oleic acid. The structure，morphology and magnetism of the composite were characterized by X-ray diffraction (XRD)，Fourier transform infrared spectroscopy (FTIR)，transmission electron microscope (TEM) and vibration showpiece magnetor (VSM). The results showed that the coated Fe3O4nanoparticles were uniform spheres and had good dispersion，and its average diameter was about 8 nm. In addition，the composite had superparamagnetism and the saturation magnetization intensity was 61.8 emu/g.

摘要： 采用微波水热法制备超顺磁性Fe3O4纳米粒子，讨论了[Fe3+]/[Fe2+]、晶化温度、晶化时间、pH值4因素对平均粒度大小的影响，探索Fe3O4纳米粒子的最佳制备条件，在该基础上采用油酸对其进行表面改性。利用XRD、FT-IR、TEM和VSM对Fe3O4纳米粒子的结构、形貌、磁性能进行表征。结果表明，改性后的纳米Fe3O4粒子为粒度均匀的球形，具有良好的分散性，平均粒径约8 nm；该产物具有超顺磁性，饱和磁化强度为61.8 emu/g。