Through establishing a test system of coaxial dielectric barrier discharge type non-thermal plasma reactor, using Q-V Lissajous figure method to measure its electrical parameters, optical emission spectrum of NO/N2 mixed gas system was analyzed, and the effects of the applied voltage peak-peak value(VP-P) on the optical emission spectrum intensity of NO, N2 excited state species were studied when NO/N2 mixture gas passed the reactor's discharge area. The results showed that high-energy electrons produced by non-thermal plasma played an effective role on the NO, N2 molecules and produced a variety of excited states matters, such as NO(A2Σ+-X2Π), N2(C3Π u→B3Π g); NO(A2Σ+-X2Π) optical emission spectrum strength firstly increased then decreased with the increase of VP-P, N2(C3Πu→B3Πg) optical emission spectrum strength increased with the increase of VP-P; in NO/N2 mixture gas system, NO was removed mainly through the reduction reaction, its removal rate could reach 98%.