In order to understand the reaction mechanisms of NO removal in Dielectric Barrier Discharge reactor, the effect of gas composition on plasma reduction of NO was studied. In this experiment, single-layer barrier tube plasma reactor was used to study the influence of O2and C2H4(ethylene) to NO removal rate. The result indicated that: with the increase of input power, NO removal efficiency increased gradually in the N2/NO system; The O2added to the gas caused removal efficiency to reduce. There was no significant effect on removal of NO with C2H4added alone. In the N2/NO/O2/C2H4gas condition, C2H4will promote the conversion from NO to NO2, the removal efficiency of NO increased as more C2H4was added. And the presence of C2H4was conductive to reduce input power.