SiC fiber was fabricated by chemical vapor deposition on tungsten filament heated by direct current in a CH(3)SiCl(3)-H(2) gas system. Microstructure of W/SiC interfacial reaction zone in the fiber was identified by means of scanning electron microscope and transmission electron microscope. Results showed that the thickness of the interfacial reaction zone is between 350 and 390 nm, and two reaction products of W(5)Si(3) and WC were formed during fabricating SiC fiber. Electron diffraction analysis and composition detection indicated that W(5)Si(3) is adjacent to tungsten core and WC is adjacent to SiC sheath, and the W/SiC interface can be described as W/W(5)Si(3)/VVC/SiC. Furthermore, the formation mechanism of the interfacial reaction zone is discussed. (C) 2010 Elsevier B.V. All rights reserved.