The work aims to explore law of influence of microwave heating temperature on synthesis of WCx/MWCNTs by preparing tungsten carbide (WCx) nanoparticles supported on multiwalled carbon nanotubes (MWCNTs). The WCx/MWCNTs nanocomposites were prepared with sodium tungstate as W source by combining molecular self-assembly technique and micro-wave heating technology. Phase composition, structure and morphology of the samples prepared under different conditions were characterized by X-ray diffractometer (XRD) and transmission electron microscopy (TEM); electrochemical properties of WCx/MWCNTs to hydrogen and methyl alcohol were tested in acidic environment by cyclic voltammetry method. WCx/MWCNTs nanocomposites prepared at the microwave heating temperature of 1000 ℃ were composed of WC, WC2 and C phases. The multiwalled structures of carbon nanotubes were well preserved and the WC particles were evenly distributed on external surface of carbon nano tubes. Particle size of the carbon nanotubes was 20~50 nm. The cyclic voltammetry test results indicated that the prepared WCx/MWCNTs had a certain catalytic effect on hydrogen under acidic conditions, but it had no obvious electrocatalytic effect on methanol. WCx/MWCNTs nanocomposites with small particle size, uniform distribution and complete multiwalled structures of carbon nanotubes can be prepared by controlling the microwave heating temperature. The prepared WCx/MWCNTs nanocomposites have certain catalytic action on hydrogen under acidic conditions and can load other metals to prepare composite catalyst.