For Fe layers covered by two-dimensional arrays of hexagonal close-packed polystyrene spheres which are hemispherically covered by Au films on the top,fine structures are observed in reflection,magneto-optical Kerr rotation and ellipticity spectra.The Kerr rotation achieves peaks or exhibits a narrow resonance-like spectral lineshape near the reflection minima,depending on the mechanism of the reflection dips.The Kerr rotation peaks and the resonance-like lineshape both are shifted with the sphere diameters.These phenomena can be attributed to the excitation of surface plasmon resonance and Fabry-Pérot modes.