<p>Optimizing alloy composition has emerged as an effective technique to further enhance the overall performance of traditional Fe–Si soft magnetic powder cores. Influences of alloy composition on the overall performance of Fe–Si powders and powder cores with similar particle size distributions were investigated. As the Si content increased from 4 to 6 wt%, the hardness of FeSi powders with good flowability increased. This, along with the introduction of light element, leads to a decrease in density and thus an increase in resistivity for powder cores. After passivation, good insulation quality ensured a similar stable effective permeability of about 60 in the frequency range of 100–1000&#xa0;kHz for all Fe–Si powder cores. Reduced saturation magnetization of Fe–Si alloy resulted in deterioration of DC bias performance of powder core with increasing Si content. Due to the lowest hysteresis loss, which was dominant in the test frequency range below 150 kHz, Fe–Si₅ powder core was found to have the lowest core loss (2496.5 mW/cm³ at 150 kHz and 100 mT). This favors the smallest temperature rise of + 4.7&#xa0;°C of Fe–Si₅ powder core when applied as an inductor. This work gained deeper insights into the relationship between alloy compositions and the mechanical, electrical, and magnetic properties of Fe–Si powder cores.</p>