Abstract: Nanoparticles Fe₃O₄ were synthesized with co-precipitation method and coated on the surface of multi-walled carbon nanotubes (MWCNTs) to prepare the magnetic Fe₃O₄-MWCNTs hybrid. The magnetic Fe₃O₄-MWCNTs hybrid was aligned in the epoxy resin under weak magnetic field (0.6 T). Alignment and dispersion of Fe₃O₄-MWCNTs were studied by transmission electron microscope (TEM). Dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and thermal conductivity were tested. As a result, nanoparticles Fe₃O₄ are coated on the surface of MWCNTs, hybrids are aligned end-to-up under 0.6 T magnetic field. Thermal conductivity is anisotropy, with lower thermal conductivity in vertical direction, while Fe₃O₄-MWCNTs hybrid has little effect on the parallel thermal conductivity. With adding Fe₃O₄-MWCNTs hybrid into epoxy resin, storage modulus decreases and loss modulus increases. In the meantime, loss factors of nano Fe₃O₄-MWCNTs/epoxy composites are higher than those of the pure epoxy resin exihibiting good damping property. When the mass ratio of Fe₃O₄-MWCNTs hybrid to epxy resin is 0.3%, loss factor is more than 0.7 and up to 1.16 at about 20 ℃.