Abstract: This work optimizes the electromagnetic properties of Fe-Si based soft magnetic composites by both modifying the composition and particle size distribution. The relationship between soft magnetic properties and microstructure is investigated. Great comprehensive electromagnetic properties can be obtained by firstly composing the Fe-Si powders with different sizes, and then partly replacing the coarse Fe-Si powder by Fe-Si-B-C amorphous powder with similar particle size. The amorphous/Fe-Si soft magnetic composites have good frequency stability within 1 MHz. When the mass ratio among Fe-Si-B-C amorphous powder, Fe-Si coarse powder, Fe-Si fine powder is 25∶25∶50, the effective permeability at 100 kHz is 47.6, the DC bias capacity at 100 Oe is 79.5%, and the power loss at 100 kHz/100 mT is 1806 mW/cm³. Compared with other reported amorphous-containing soft magnetic composites, the amorphous Fe-Si-B-C/Fe-Si soft magnetic composites in this work have significant advantages in cost and combined electromagnetic properties. The Fe-Si fine powder can fill the gap between the coarse powder, which is conducive to improving the density and permeability of the soft magnetic composite, while the addition of amorphous powder can significantly reduce the power loss. The amorphous/Fe-Si soft magnetic composites prepared in this work have good comprehensive electromagnetic properties and can provide potential solutions for industrial production.