A new kind of magnetic rubber was prepared by doping Fe3O4 nanoparticles into nature rubber matrix, which was characterized by the scanning electron microscopy and X-ray spectroscopy. They showed that the Fe3O4 nanoparticles were well dispersed in rubber matrix. Furthermore, the mechanical and magnetic properties of the magnetic rubber were investigated, indicating the improvement of tensile strength from 13.9 to 15.8 MPa and high saturation magnetization (16.7 emu/g) compared with the nature rubber. What' more, the loss factor of magnetic rubber treated by an external homogenous magnetic field (1.5 T) was improved from 0.07 to 0.15 compared with magnetic rubber without treating by the magnetic field. The result is attributed that after applying a magnetic field, magnetic nanoparticles on the rubber matrix are magnetized; meanwhile, magnetic dipole moments are induced, which causes magnetic field and can absorb shock energy.