Magnetite CoFe 2 O 4 nanoparticles were modified by a new series of fluorine-containing polymeric dispersants. The Fourier transform infrared spectroscopy (FTIR) and element analysis showed that the polymer chains have been successfully adsorbed onto the surfaces of the CoFe 2 O 4 nanoparticles. The influence of the content of fluoroalkyl groups on the surface tension and the dispersing properties were also investigated and the results showed that the modified CoFe 2 O 4 nanoparticles exhibit excellent surface active properties and the nanoparticles can be dispersed very well in the aqueous phase. Zeta potential and the average diameter of the nanoparticles can reach to −68mV and 42nm with the increasing of the content of fluoroalkyl groups of the polymeric dispersant, respectively.