In order to achieve better chemical absorption of NOx and SOx, oxidation of NO in the process of simultaneous desulfurization and denitrification of the flue gas based on ozone oxidation was studied. The main investigations focused on factors affecting NO oxidation including the molar ratio of O-3/NO (MR) (0.6-1.2), the oxidation temperature (65-150 C), the initial NO concentration (100-500 mg/Nm(3)), the presence of SO2 (1000-5000 mg/Nm(3)), the content of water vapor (5-15 %) and the residence time (0.07-1.8 s). The results indicated that MR had a substantial effect on NO conversion and the products of NO oxidation by 03 varied with the change of MR. When MR <= 1, the NO conversion increased from less than 60 % to more than 95 % with the increase of MR, and the oxidation product was mainly NO2. When MR( O-3 /NO) > 1, the NO conversion rate (about 97 %) basically remained unchanged, and the oxidation products under these circumstances were mainly NO2 and N2O5. When the oxidation temperature rose from 65 to 150, the conversion of NO was almost unchanged. Besides, the NO initial concentration, the presence of SO2, the water vapor content and the length of the flue gas outlet pipe had negligible impact on the NO conversion within the range selected for the study. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.