Nitrogen oxides (NO + NO2) in most practical exhaust gases is mainly composed of NO. The injection of ozone, produced by dielectric barrier discharge, into the exhaust gas gives rise to rapid oxidation of NO into NO, Once NO is converted into NO2, it can readily be reduced to N-2 by a reducing agent in the next step. Sodium sulfide (Na2S) used as the reducing agent can also remove SO2 effectively, which makes it possible to treat NO. and SO2 simultaneously. The present two-step process through an ozonizing chamber and an absorber containing a reducing agent solution was able to remove about 95% of the NO. and 100% of the SOP initially contained in the simulated exhaust gas. The formation of H2S from sodium sulfide was able to be suppressed by a basic reagent. The use of NaOH and CaCO3, together with the reducing agent not only prevented H2S from forming, but also cut down on the consumption of the reducing agent.