NO removal from flue gas was conducted on a self-made bubbling reactor with ClO2. Results indicated that ClO2 has excellent oxidizing power to NO, and its actual reaction molar ratio is close to the theoretical molar ratio. At the temperature of 80 degrees C and ClO2/NO = 0.6, the NO removal efficiency can reach 96.7%. The electron spin resonance and inhibitor (sodium formate and isopropanol) addition experiments indicated that the ClO2 and center dot OH radical in the solution played an important role in NO oxidation. The mechanism of NO removal by ClO2 was proposed through the analysis of oxidation products and relative references.