In order to discover main reaction mechanism of CH4 in NOx removal by methane reburning, reactions between CH4 and NOx were simulated from the point of reaction kinetics. Simulating result demonstrated that reaction temperature and excessive air coefficient were main factors influencing DeNOx efficiency. NO could be directly reduced by free radicals including H, HO2, HCCO and O. Firstly, NO was mainly reduced by HO2.Secondly,NO was mainly reduced by H. Hydrocarbon radicals such as CH3, CH2, C2H4, CH2O, C2H6, CH2CO, HCN, HCNO, HNCO were produced in reaction processes as intermediate products. Lots of free radicals were consumed or produced in reaction and led to concentration variation of NO. At the same time, NO could be directly reduced by hydrocarbon radicals such as CH3, CH2.Therefore, hydrocarbon radicals have important influence on removal efficiency of NOx during methane reburning.