Abstract. In this study, an experimental apparatus of oxidation + absorption columns was set up to investigated ClO 2 and Cl 2 emission characteristics when NaClO 2 was used as oxidant. Two sets of experiments were designed and compared, one was sampled every 15 min for 2 h and the other one was continuous sampling for 2 h. The results show that the concentration of ClO 2 in the outlet of oxidation column increased first and then decreased while Cl 2 barely changed during the experiment. The concentration of Cl 2 was far less than ClO 2 , which indicated that the chlorine-containing gaseous component was mainly in the form of ClO 2 . After 2 h reaction, the chlorine-containing ions in oxidation liquid before and after reaction were in good consistence with the theoretical calculation. High concentration of Cl -was detected in the absorption liquid, while no ClO 2 -and ClO 3 -existed. As the reaction proceeded, the oxidation liquid gradually turned into light yellow, and pungent odor released.