Both NOx conversion and CO2 conversion decrease with increasing percent-level CO2 concentration in nonthermal nitrogen plasma. The rate constants of electron collision reactions of both N-2 and CO2 decrease with increasing CO2 concentration because electronegative CO2 reduces electron concentrations in the reactor due to the electron attachment process. The rate constant of CO2 dissociation through electron collision is 1-2 orders of magnitude higher than that of N2 dissociation because of low dissociation energy Of CO2. Model data for reactor outlet NO., and COx concentrations agree well with experimental data. The effect of CO2 on NO, NO2, N2O, and CO concentrations can be explained on the basis of the proposed reaction mechanism and kinetic modeling.