To decompose carbon dioxide, which is a representative greenhouse gas, a 3-phase gliding arc plasmatron device was designed and manufactured to examine the decomposition of CO2, either alone or in the presence of methane with and without water vapour. The changes in the amount of carbon dioxide feed rate, the methane to carbon dioxide ratio, the steam to carbon dioxide ratio, and the methane to steam ratio were used as the parameters. The carbon dioxide conversion rate, energy decomposition efficiency (EDE), carbon monoxide and hydrogen selectivity, and produced gas concentration were also investigated. The maximum values of the carbon dioxide conversion rate, which is a key indicator of carbon dioxide decomposition, in different cases were compared. The maximum carbon dioxide conversion rate was 12.3 % when pure carbon dioxide was supplied; 34.5 % when methane was injected as a reforming additive; 7.8 % when steam was injected as a reforming additive; and 43 % when methane and steam were injected together. Therefore, this could be explained that the methane-and-steam injection showed the highest carbon dioxide decomposition, showing low EDE as 0.01 L/min W. Furthermore, the plasma produced carbon-black was compared with commercial carbon-black chemicals through Raman spectroscopy, surface area measurement and scanning electron microscopy. It was found that the carbon-black that was produced in this study has the high conductivity and large specific surface area. Our product makes it suitable for special electric materials and secondary battery materials applications.