In this work, the high-frequency response of the Salisbury screen made of metallic thin film was investigated. The formulas of reflectivity and bandwidth coefficient were derived. Theoretical and numerical studies show that the spectrum of reflectivity presents a resonance type, which is symmetric to the resonance frequency. The reflectivity is determined only by the normalized surface resistance α of the metallic film at resonance, and by both α and wave impedance η2 of the isolation layer at other frequencies. For the bandwidth coefficient Δ, it is determined by the examined reflectivity Γa, η2 and α. Bandwidth coefficient can be improved by changing the wave impedance η2, and tuning the surface resistance to the optimum value αc which is correlated to Γa and not equal to the one in most cases. It is also noted that the thickness of the metallic thin film should be in the order of sub-micron or nanometers.