In order to adjust the initial permeability and the dielectric constant for suppressing electromagnetic interference (EMI), a series of the composites with Pb0.95Sr0.05(Zr0.52Ti0.48)O3 (PZTS) powders and NiCuZn ferrite (NCZF) powders as raw materials were synthesized by a solid-state reaction method. The effects of different PZTS content on the sintering behaviors, phase composition, microstructures and electromagnetic properties of the composites co-fired at 900 °C were investigated. The acquired ferroelectric–ferromagnetic composites are of perovskite phase and spinel phase, exhibiting both capacitance and inductance properties and excellent frequency stability due to the mutual effects of magnetization of NCZF phase and the polarization of PZTS phase. As PZTS content increased, the initial permeability and the saturation magnetism (Bm) decreased gradually, the coercive force (Hcb) and the quality factor (Q) increased, the resonance frequency shifts toward a higher frequency. Simultaneously, the dielectric constant evidently increased with PZTS content when x varied from 0 to 50 wt%. A maximum Q-factor (50), a maximum dielectric constant (80), a higher DC resistivity (4.96 × 1010 Ω m), a higher ferromagnetic resonance frequency (over 1.8 GHz) and a relatively higher initial permeability (5–7) were obtained for the composite with 50 wt% PZTS.