Abstract: Soft magnetic multi-component alloys not only exhibit excellent soft magnetic properties but also possess high-temperature stability, high corrosion resistance, and high mechanical properties. Soft magnetic composites (SMCs) prepared therefrom are expected to combine high-power density, high energy conversion efficiency, and excellent service properties. In this work, multi-component amorphous Fe₇₇Ni₆Cr₂Si₂P₁₁B₁C₈Nb₁ magnetic powders were prepared via gas-water combined atomization. Meanwhile, new SMCs were fabricated through structural design of the insulating layer and process optimization. The correlation mechanisms between the insulation process, microstructure, and electromagnetic properties of SMCs were systematically investigated. Compared to the Fe₇₇Ni₆Cr₂Si₂P₁₁B₁C₈Nb₁SMCs coated solely with a silicone resin layer, when a uniform and continuous SiO₂ layer is deposited on the surface of the magnetic powder via atomic layer deposition, the resistivity of the coated powder is significantly increased, while the conductivity is reduced. The effective insulation between magnetic powders can effectively suppress eddy current loss, which further enhances the frequency stability of the SMCs. Optimized electromagnetic properties have been achieved for the Fe₇₇Ni₆Cr₂Si₂P₁₁B₁C₈Nb₁@SiO₂ SMCs, including an effective permeability of 33 with a high frequency stability up to 5000 kHz, high quality factor of 162, low total core loss of 98.7 mW/cm³ at 100 kHz for 50 mT, which is expected to satisfy the performance requirements of SMCs for high-power devices.