The composition design rules for high Bs amorphous alloys are introduced from the binary phase diagram, atomic size and the effects of amorphous forming elements on magnetic performance and ribbon manufacturability. The effects of metalloid elements on amorphous-forming ability and magnetic properties as well as origin of the excellent properties for high Fe content Fe83(Si,B,P,C)17 amorphous alloys are explored. Based on the similar Fe content of Fe–B, Fe–P and Fe–C eutectic alloys, the alloy systems with the combination of Fe, B, P, C and Si are beneficial to the achievement of high Bs and amorphous-forming ability. With the addition of Si, P and C in Fe83B17, the amorphous-forming ability and the soft-magnetic properties improve clearly. The critical wheel speed decrease from 54 m/s to 12 m/s and the maximum thickness increase to 76 μm. The improvement of the amorphous-forming ability is discussed in term of the competition effect and the eutectic theory.