A DBD-type (dielectric barrier discharge) NTP (non-thermal plasma) reactor wasdesigned and an experimental system was established, in order to study the mechanism of plasmachemistry reactions in a gas mixture of C_3H_6/NO/O_2/N_2. This paper is focused on a. the effectsof the initial concentrations of both NO and O_2 upon NO conversion rate and the variations ofNOx and O_3 concentrations versus SED (specific energy density) when mixed gases of NO/O_2/N_2passed the NTP reactor; b. the effects of the initial concentration of C_3H_6 upon NO oxidationand reduction reactions in mixed gases of NO/N_2/C_3H_6 and NO/N_2/O_2/C_3H_6. The conclusionsdrawn are as follows, a. When the mixed gases of NO/O_2/N_2 passed the NTP reactor, NO wassimultaneously involved in oxidation and reduction reactions with the former dominant and NO_2concentration increased at the NTP reactor outlet. The NO conversion rate decreased with theincrease of the initial concentration of NO and O_2, the O_3 concentration firstly increased andthen decreased with the increase in SED value, b. NO reduction reaction was very weak andenergy consumption was very high in a mixed gases of NO/N_2. However, when C_3H_6 was added,the NO conversion rate was significantly increased. When C_3H_6 was added to the mixed gases ofNO/O_2/N_2, the NO conversion rate was significantly increased and the energy consumption wasconsiderably reduced. A DBD-type (dielectric barrier discharge) NTP (non-thermal plasma) reactor was designed and an experimental system was established, in order to study the mechanism of plasma chemistry reactions in a gas mixture of C_3H_6 / NO / O2 / N2. This paper is the effects of the initial concentrations of both NO and O_2 upon NO conversion rate and the variations of NOx and O_3 concentrations versus SED (specific energy density) when mixed gases of NO / O_2 / N_2passed the NTP reactor; b. the effects of the initial concentration of C_3H_6 upon NO oxidation and reduction reactions in mixed gases of NO / N_2 / C_3H_6 and NO / N_2 / O_2 / C_3H_6. The conclusions drawn are as follows, a. When the mixed gases of NO / O_2 / N_2 passed the NTP reactor , NO wassimultaneously involved in oxidation and reduction reactions with the former dominant and NO_2concentration increased at the NTP reactor outlet. The NO conversion rate decreased with theincrease of the initial concentration of NO and O_2, the O_3 concentration fi rstly increased and decreased with the increase in SED value, b. NO reduction reaction was very weak an energy consumption was very high in a mixed gas of NO / N2. However, when C_3H_6 was added, the NO conversion rate was significantly increased. When C_3H_6 was added to the mixed gases of NO / O_2 / N_2, the NO conversion rate was significantly increased and the energy consumption wasconsiderably reduced.