Ni 0.45 Zn 0.55 Fe 2 O 4 (40nm) single-layer and Fe 50 Mn 50 (25nm)/Ni 0.45 Zn 0.55 Fe 2 O 4 (40nm) bilayer films were prepared on Si(111) substrates by radio frequency magnetron sputtering at room temperature, and the influence of FeMn underlayer on the microstructure and magnetic property of Ni–Zn ferrite film has been investigated. It was found that the introduction of Fe 50 Mn 50 underlayer resulted in a decrease from 7.1 to 3.1kA/m in coercivity and increase from 0.22 to 0.60 in residual magnetization ratio of the ferrite film. The complex permeability μ=μ′−iμ″ values of the films were measured at a frequency of up to 5GHz. An obvious resonance peak at about 1.65GHz of the bilayer film appeared in the permeability spectrum. The reason has been researched preliminarily and was ascribed to the change of the film's microstructure with FeMn underlayer.