Microwave discharge plasma using catalyst-assisted active coke (Fe/AC, Mn/AC, Cu/AC) provides high performances for NO reduction at lower power (200 W) in this study. Results show that the effect of plasma and catalysis not only enhances the ability of plasma to remove NO, but also reduces the energy consumption of reaction; especially, Fe/AC increased the removal efficiency by nearly 64.8% compared with original coke. Plasma intensity was enhanced with the polarization increased by catalysts, giving better denitration performance. All the metal oxides studied catalyze the NO-carbon reaction, and the metal oxides had the tendency to be reduced. What is more, the catalysts increase the polarization of active coke, accelerating the rate of the temperature rise in the microwave field and increase the content of oxygen-containing functional groups, thereby promoting the C-NO reaction.