Since the magneto-optical Kerr effect plays an important role in the technology of detecting thin film magnetism, and the current detection technology has problems such as poor magneto-optical Kerr signals as well as large frequency of change, how to enhance the Kerr response of magneto-optical materials has become an important issue in today’s scientific research. A three-layer plasma hybrid microstructure covered with “L”-shaped periodic aluminum blocks aiming for Kerr response enhancement is proposed. In the near-infrared wavelength range of 0.6 to 1.1 μm, by varying the size of the opening and width of the upper aluminum film, a maximum polar magneto-optical Kerr rotation angle of 11.08 deg was obtained in a bismuth iron garnet film with thin films and accompanied by a high reflectance. The effects of different opening sizes, widths, incidence angles, magnetic field sizes, metal materials, and magneto-optical materials on the structure were also investigated. The results show that the structure can both increase the Kerr rotation angle by adjusting the magnetic field and incidence angle as well as combine different plasma metals to enhance the magneto-optical Kerr effect, which improves the universality of engineering applications. In addition, the electric field contours at the intersection of different materials are given and the physical mechanism of the enhanced polar magneto-optical Kerr rotation effect is explained. The results of this work will provide some guidance and help for the amplification of experimental measurement signals of the Kerr effect and the design of tunable magneto-optical Kerr devices.