Abstract: FeSiAl (FSA) alloys, as the typical magnetic wave-absorbing materials, demonstrate the potential for application in marine equipment stealth and protection. However, the practical engineering use is severely constrained by inherent low-frequency impedance mismatch and high electrochemical activity. The flake-shaped FSA micro-powders were modified using air/argon plasma treatment in this paper. The surface morphology and compositional changes of the FSA micro-powders were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), and X-ray photoelectron spectroscopy (XPS). Combined with the electrochemical tests and vector network analyzer (VNA) measurements, the synergistic regulation mechanism between corrosion behavior and low-frequency electromagnetic wave loss performance of the FSA micro-powders was systematically investigated. The results show that, the plasma treatment in different atmospheres does not significantly alter the composition of the FSA micro-powders, but primarily affects the surface microstructure of FSA. The FSA micro-powders treated in the air atmosphere (FSA-Air) exhibit the rich fibrous structure, while the FSA micro-powders treated in the argon atmosphere (FSA-Ar) mainly show the granular structure. At the thickness of 5 mm, the FSA-Air micro-powders achieve the effective absorption bandwidth of 0.36 GHz (0.59~0.95 GHz) and the minimum reflection loss of –16.65 dB, significantly outperforming the untreated FSA. Additionally, the corrosion resistance of the FSA-Air micro-powders is notably improved, with the corrosion current density decreasing from 7.25×10^–6 A·cm^–2 to 1.85×10^–6 A·cm^–2.