Nanometer magnetic particles were prepared through oxidizing Fe2+ in basic solution. Initially, using resultant nanometer magnetic powder as support, supported nanometer magnetic Ziegler-Natta catalysts were obtained. Through polymerization in situ on the surface of nanometer magnetic particles, a new kind of magnetic polyolefin that is different from both the composite plastics＇ magnet and the structure plastics＇ magnet was obtained.