FeWB alloy powders were successfully produced by reactive synthesis. In this paper, effects of particle size of raw materials on the synthesis behavior of FeWB alloy powders were systematically investigated and powders with a high density of 13.99 g/cm(3) were fabricated into bulk materials by Spark Plasma Sintering (SPS) technique. Both W and FeB with varying particle sizes ranging from 3 mu m to 15 mu m were used as raw materials to prepare FeWB alloy powders. Microstructural analysis was performed using X-ray diffraction (XRD), scanning electron microscopes (SEM) equipped with an energy dispersive spectroscopy (EDS), and Mossbauer spectrometry at room temperature. Mean particle sizes were determined by laser granulometry. The results showed that particle size of raw materials had noticeable influence on both microstructure and amount of the resultant FeWB powders. Hardness of the bulk materials was measured by HR-150A Rockwell hardness tester. It had been significantly enhanced and reached 91.8 HRA, which could be comparable to that of cemented carbides. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.