Magnetic properties are perhaps the most remarkable and unique properties of Fe-based amorphous alloys. To obtain high saturation magnetization, high Fe content is preferred. However, there is a strict upper limit of Fe content for the formation of a single amorphous structure with good magnetic softness. Fe-based amorphous alloys with high Fe content over the limit have an as-quenched structure consisting of coarse alpha-Fe grains in an amorphous matrix, which inevitably results in inferior magnetic softness. We have studied the effect of P and/or Cu additions on the microstructure of Fe-based amorphous alloys with high Fe content. The alpha-Fe grain size and the coercivity (H-c) decrease by the simultaneously adding P and Cu. The Fe-rich FeSiBPCu alloys with the optimized composition have an extremely small alpha-Fe-like phase of about 3 nm or smaller in a diameter, exhibits the higher J(s) of about 1.67 T than that of the typical Fe-based amorphous alloy and show the low coercivity (H-c) of about 4 Am-1 in an as-quenched state. [doi:10.2320/matertrans.ME200831]