Abstract: Taking 700×10³ m³/h sintering flue gas as an example, the ozone oxidation and absorption of NO_x by semi-dry method in practical engineering application was studied. The results showed that the reaction of ozone and NO in flue gas was very fast. The key factor of ozonation was to improve the distribution of ozone in flue and increase the utilization rate of ozone. The reaction temperature had significant effect on the absorption of NO_x. With the increase of temperature in desulfurization tower, the absorption efficiency of NO_x decreased continuously. When the temperature was higher than 95 ℃, the denitration efficiency was dropped to 0. However, the denitration efficiency could be improved by increasing the amount of lime and ozone. From the operation of the process, the cost of denitration was not high. The process is worthy to be popularized and applied.