The effects of element addition, Co, Cu, and Ag on the microstructure, thermal property and magnetic properties of mechanical alloyed FeSiBAlNi high entropy alloys (HEAs, base alloy) have been investigated in depth in the present work. The FeSiBAlNi (Co, Cu, Ag) amorphous HEAs have been successfully fabricated by mechanical alloying process. The results reveal that Co and Cu additions obviously shorten the formation time of fully amorphous phase, therefore, leading to enhanced glass forming ability of the base alloy. The final milling product of FeSiBAlNiAg consists of amorphous phase and nanocrystals with face-centered cubic (FCC) structure. In addition, Co addition obviously improves the thermal stability of the base alloy, while Cu and Ag additions present the detrimental effects. Moreover, the as-milled HEAs exhibit the semi-hard magnetic property. However, the saturation magnetization (M-s) values become decreased with element additions. It suggests that the coexistence of FCC and body-centered cubic (BCC) phase gives rise to a higher M-s than a single amorphous phase or mixture of amorphous and FCC phases. Additionally, the phase formation mechanisms of amorphous and solid solution phases, as well as the correlation between the microstructure and magnetic properties have been discussed, which can be beneficial to the design of novel alloy systems. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.