We synthesized a nanoferroferric oxide materials using a chemical coprecipitation method and propose a technique to depress the low density lipoproteins in the blood.the physical and biological properties and toxicity of the materials are studied,their scales are in the range of 50-60 nm.From infrared absorption spectrum with characteristic wavenumbers at 580cm-1 and 1624cm-1 we determine that the nanoFe3O4 includes some hydroxyls; The thermal stability and firmness degree of the dextran sulfate is grafted onto the surface of the nanoFe3O4 powders are determined by infrared spectrum of absorption,this result shows that the complex is very stable and not dissociated,when it is heated and circumfluenced about 20 minutes at 60℃ under the alkalinity conditions produced by NaOH,their grafting mechanism is due to the dipole-dipole or hydrogen bond interactions between them.