Abstract: Fe₃O₄ nanoparticles were prepared by a precipitation method. The Fe₃O₄ nanoparticles were dealt with ethanol to form an organic surface. Then polypyrrole composite was polymerized by the emulsion polymerization method in the presence of these Fe₃O₄ nanoparticles. The structural characterization by TEM, XPS, and AAS proved that the dispersion of Fe₃O₄ nanoparticles dealt with alcohol was better than that of naked ones. Fe₃O₄ nanoparticles were entrapped or encapsulated in the PPy chain. The thickness of the PPy layer was about 10 nm. The Fe₃O₄ / PPy composites showed electrical and ferromagnetic property( e= 7. 69 s/ cm～13. 6 s/ cm, M_s= 12. 06 emu/ g～24. 38 emu/ g, H_c= 11 Oe～41 Oe) . The environmental stability of composites was better than that of PPy.