In diesel engine, generally, the removal of carbon nanoparticles has been based on a filtration system or oxidation reactor with O2 at high temperatures of above 800 °C. Recently, NO2 has been found to be a more efficient oxidant than O2 at lower temperatures in the range of 200~500 °C. Small amounts of NO2 in the range of a few hundreds of ppm by volume can promote the continuous oxidation of carbon particulates. Thus far, experiments involving diesel PM (particulate matter) oxidation by NO2 are only practiced as regards the soot deposited on filters or plates. However, in aerosol state, depending on the surrounding temperature and the NO2 concentration, the carbon nanoparticle removal rate is significantly different. Therefore, the study of nano-sized carbon aerosol oxidation in various gas circumstances is required. In this study, the oxidation characteristics of nano-sized carbon aerosol particles in NO2 condition are investigated.