Abstract: In order to develop a method which can convert CH4 and CO2 obtained from biomass pyrolysis into syngas production, the reforming of CH4 with CO2 by a biomass char was conducted with microwave heating in this paper. The influences of particle diameter, microwave power, the molar ratio of CO2 and CH4 as well as the volumetric hourly space velocity on the CH4 and CO2 conversions were investigated, and the behaviors of CH4 decomposition, the reforming of CH4 with CO2 and CO2 gasification reaction were studied. The results indicate that reactant gases conversions are found to be almost unchanged when the particle diameter is below 0.83 mm. And increasing microwave power, enhancing the molar ratio of CO2 and CH4 or reducing the volumetric hourly space velocity result in an increase in the reactant gas conversions. In the reforming reaction, higher conversions of CH4 and CO2 can be obtained at the beginning, and then the CO2 conversion is decreased slightly, together with a sustained decrease in the CH4 conversion. Compared to the reforming reaction, more significant decrease in the CH4 conversion is observed in the CH4 decomposition reaction. The initial CO2 conversion in the gasification reaction is higher than that in the reforming reaction, and then it is lower than that in the reforming reaction after 60 min. The results indicate that biomass char has a good catalytic effect on the reforming of CH4 with CO2 under microwave irradiation.