Electrical discharges triggered by microwave-metal interactions are important phenomena in microwave heating processes with the generation of plasma. In this study, microwave-metal (MW-m) discharge was developed for tar destruction. Toluene was used as a tar model compound. Uniform tungsten electrodes was adopted and optimized to provide a fast-ignition, relatively-stable and sustainable discharge process. The conversions of toluene were investigated at different gas flow rates and preliminary tests were conducted to in-situ eliminate the generation of solid carbon. Microwave-tungsten discharge can effectively destruct toluene into useful gases (H-2, C2H2 and CH4) and solid carbon, with a high conversion efficiency of more than 90%. The generated solid carbon can be effectively eliminated by introducing water steam into the discharge reaction to achieve a comparable toluene conversion efficiency of 92.3% and a production of syngas (H-2 to CO ratio is around 1.6). This work can offer important reference for developing a new technology for tar cracking in a biomass gasification process. (C) 2017 Elsevier Ltd. All rights reserved.