The purpose of this study is to observe the purification characteristics of NOx, CO and HC in various catalysts and excess air ratio conditions. For this purpose, we installed various catalysts on the back stream of the coaxial diffusion burner with swirler. As the result, in the case of NOx, Pt-Rh catalyst shows very high value that is more than 90%-conversion efficiency without the relation with the excess air ratio. After excess air ratio of ${alpha}=1.14$, it shows that the conversion efficiencies were more than 80% in the every Pt catalyst in the view of conversion of every exhaust with changing of the excess air ratio.