ABSTRACT Magnetic polymer nano-copmposites recently received growing attention due to the fact that such composite particles offer potential advantages in wide applications. The present study describes a method for the preparation of three different types of magnetic core-shell nono-composites (diameter is 50-100 nm) of magnetite polyvinylbenzyl chloride, n magnetite polyvinyl aniline and bi-layered polymer magnetite with (-Cl, NH2 ad –OH) functional groups respectively.The first two types of magnetic core-shell nano-composites have hydrophobic properties, preparation is based on several steps: precipitation of the magnetic iron oxide by a coprecipitation process leading to particles with superparamagnetic properties (diameter is 10–20 nm), coating the magnetite with oleic acid as stabilizing agent and finally the encapsulation of magnetite into the first hydrophobic polymer shell by miniemulsion polymerization. The third type of magnetic core-shell nano-composites with hydrophilic properties is prepared by the costing of magnetite polyvinylbenzyl chloride with a hydrophilic layer of polyethylene glycol (PEG) by condensationpolymerization.Vinylbenzytl chloride and vinyl aniline were chosen as hydrophobic monomers because they offer the possibility to anchor additional functional groups for active site attachment and protect magnetite against chemical attack. For the miniemulsion polymerization the influence of the amount of wate, the mixing intensity and the surfactant concentration were studied with respect to the formation of particles which can further be used for chemical engineering applications and for binding enzymes on the functionalized surface sites.The resulting magnetic polymer nano-composites were characterized by particle size measurement (Malvern Zeta sizer), chemical stability (acid treatment with hydrochloric acid), iron content (elemental analysis by wet chemistry) and morphology (transmission electron microscopy (TEM), function groups (infrared spectrometer ( IR) and proton NMR spectroscopy (H-NMR). Finally auger electron microscopy (AES) was used to measure elemental profiles across the composite particle diameter.