Spherical Fe3O4@SiO2 nanoparticles with good dispersibility (denoted as S1) were prepared by Stöber hydrolysis⁃polycondensation method, and the particle size was 300～430 nm.In order to investigate effect of carbon number in the organosilicone on 51 hydrophobicity and demusification of magnetic nanoparticles, the methyl triethoxysilane, n⁃hexyltriethoxysilane, n⁃dodecyltrimethoxysilane and n⁃octadecyltriethoxysilane were used to modify the surface of the S1 respectively, and the products were marked for S2—S5. The magnetic samples were characterized by electron microscopy (TEM), scanning electron microscope (SEM), X⁃ray diffraction (XRD), fourier transform infrared (FTIR) spectra and thermogravimetric analyses (TGA). The static water contact angle of magnetic nanoparticles (θW) were 10.6º、42.6º、113.6º、128.0º and 148.3º for S1—S5 respectively, and the results indicated that the θW increased with carbon number in the silane coupling agent increasing. Besides, the hydrophobic coating amount on the S1 surface of S2—S5 were estimated to be 0.005, 0.087, 0.092 g/g and 0.087 g/g respectively. The samples can be applied to removal the oil from water surfaces. Four kinds of silicone⁃modified magnetic particles can remove the surface oil, the n⁃dodecyltrimethoxysilane modified magnetic particles have the best effect of removing oil.