In search of next-generation optical information functional materials, magneto-optical microstructures have attracted great attention since they can break Kirchhoff’s law and produce higher photoelectric conversion efficiency. Theoretical studies using finite-difference time-domain and transfer matrix methods have been performed to investigate the optical properties of magneto-optical microstructures. However, these methods are computationally intensive and require periodic conditions, which may not be satisfied with most fabricated samples. The equivalent medium algorithm is improved to make it suitable for the equivalent of magneto-optical materials. Based on the improved equivalent medium theory (EMT), a magneto-optical InSb film structure doped with Au particles (D-InSb) is designed. The effective dielectric functions of the D-InSb layer for transfer matrix waves are obtained from the Bruggeman approximation. Thin-film optics formulas incorporating the anisotropic wave propagation in uniaxial media are employed to calculate the nonreciprocal absorptance of the D-InSb film. The effect of geometric parameters, such as filling ratio and number of layers, is investigated. In addition to modeling the directional radiative properties at various angles of incidence, the hemispherical properties are also calculated to understand the light absorption. The results of our study can provide methods and ideas for the design of solar cells, infrared absorbers, and optical isolators.