The characteristics of NO oxidation using sodium chlorite (NaClO2) powder have been investigated by a flow type packed-bed reactor, where the reaction temperature and the space velocity are varied in the range of 20~230 oC and 0.4-2.2×105 hr-1, respectively, and the simulation gas mixtures are composed of NO (0~200 ppm), NO2 (0-200 ppm), O2 (0~15%) and H2O (0~15%) within N2 balance. It has been found that the oxidation efficiency of NO depends greatly on the reaction temperature, exhibiting the existence of critical reaction temperature at about 170 oC where the oxidation efficiency of NO is maximized and then abruptly decreased with further increase of reaction temperature, resulting in being negligible over 190 oC. Such a behavior in the oxidation efficiency has been originated from the phase transition of NaClO2 at about 170 oC to form NaClO3, and NaCl which are chemically inactive toward the oxidation of NO. The chemical reaction of NO with NaClO2 has been observed to produce NO2, ClNO and ClNO2, whereas that of NO2 only OClO species. Additionally, we have also observed that the introduction of O2 and H2O has little influence on the oxidation of NO.