The invention discloses a strong magnetic film medium, which has a laminated structure consisting of a buffer layer, a permanent magnetic film and a protective layer on a substrate material. A preparation method comprises the following steps of: firstly, preparing a clean and dry Si substrate, and growing and preparing the buffer layer on the surface of the substrate; secondly, preparing the permanent magnetic film and the protective layer with geometrical shapes in turn on the buffer layer by adopting a mask growth method or a growth ablation method under a vacuum condition; and finally, magnetizing the film medium by using a magnetizer. The application of the technical scheme of the invention reduces the size of a permanent magnetic material to micron magnitude; and the film medium generating a large magnetic field has the advantages of small volume, high magnetic field strength, good magnetic field directivity, simple design, high reliability and the like. In addition, the method for preparing the film medium has the advantages of simple process and broader application field.