Carbon dioxide reforming of methane via dc corona discharge plasma reaction at atmospheric pressure has been investigated. The effects of the CH4/CO2 ratio in the feed, flow rate, discharge power, and corona types have been systematically studied. The results show that the molar ratio of H-2 to CO in the products strong depends on the molar ratio of CH4 to CO2 in the feed. The discharge power, flow rate, and corona types have slight influence on the syngas composition. When the CH4/CO2 ratio is 1/2, the syngas of lower H-2/CO ratio at about 0.56 is obtained, which is a potential feedstock for synthesis of liquid hydrocarbons. The conversions of methane and carbon dioxide increase with increasing the discharge power and decrease with increasing the flow rate. The conversions of reactants via positive corona are generally higher than that via negative corona, but the ratio of H-2/CO in the products is the other way round. Besides syngas and water, other products including various hydrocarbons and oxygenates are detected by a quadrupole mass spectrometer. There is visible coke mainly depositing on the cathode when the CH4/CO2 ratio is higher than 2/1. We propose that the coke mainly formed via methane decomposition during the reaction.