A rotating gliding arc (RGA) reactor was investigated for conversion of multiple model tar compounds including toluene, naphthalene, and phenol in simulated synthetic gas, with special focus on the effects of steam concentration (0-20%) and preheating temperature (300-700 degrees C). The maximum conversions of toluene, naphthalene, and phenol were 89.3%, 84.6% and 95.5%, respectively, at a steam concentration of 12% and a preheating temperature of 500 degrees C. The tar conversion reaction facilitated the formation of fuel gas H-2 and CO and reduced the CH4 and CO2 content, thus increasing the heating value of the simulated synthetic gas, by a maximum of 5.1% at a steam concentration of 20%. The results indicated that the RGA plasma is promising for achieving efficient conversion of tar of complex composition in high temperature simulated synthetic gas and upgrading gaseous products.