An AC-pulsed tornado gliding arc plasma was employed for CO2 conversion via CO2 decomposition and dry reforming reactions. A stable and high-efficient constant arc length discharge mode was obtained in this plasma reactor. And then, CO2 conversion was studied under this discharge mode. In the case of CH4/CO2 = 0, CO2 was converted to CO and O-2 via the CO2 decomposition reaction. Energy efficiency of 29 % was attained at CO2 conversion of 6 %. With strong reducing agent CH4 added into CO2, the main contributor of CO2 conversion changed from CO2 decomposition to dry reforming of CH4. Conversions of CH4 and CO2, energy efficiency and energy cost changed sharply at CO2/CH4 ratios lower than 1/4, while they changed slowly at CH4/CO2 ratios above 1/4. In the case of CH4/CO2 = 2/3, energy efficiency of 68 % and syngas energy cost of 1.6 eV/mole were achieved at CH4 conversion of 29 % and CO2 conversion of 22 %.