The wear behaviors of 45 steel were investigated on homemade tester under magnetic field. By using Scanning Electron Microscope (SEM) and X-ray diffraction (XRD), the worn surface was analyzed. The result shows that after applying the magnetic field, both the wear rate and the friction coefficient of the sample are decreased; the accumulation and oxidation of wear debris on the worn surface are the main reasons for the magnetic field to improve the friction and wear properties of steel.