Abstract: The effect of SO₂ on the reduction of NO by methane over iron and iron oxides was investigated at 300~1 100 ℃ in an electrically heated ceramic tubular flow reactor in simulated flue gas and N₂ atmosphere. The iron catalyst after reaction was characterized by X-ray diffraction (XRD) and the mechanism of NO reduction by methane over iron catalyst in the presence of SO₂ was elucidated. The results demonstrated that methane is effective to reduce NO over iron and iron oxides and SO₂ in the flue gas has little influence on the reduction of NO. In N₂ atmosphere with 0.01%~0.04% SO₂, metallic iron can simultaneously eliminate almost 100% of NO and SO₂ at a temperature above 700 ℃. In the simulated flue gas with 0.01%~0.04% SO₂, the efficiencies of NO reduction at 850 ℃ and 950 ℃ are higher than 95% and 98%, respectively; the influence of SO₂ on NO reduction is insignificant. More than 95% of NO is reduced by 1.13% methane over iron at 1 000 ℃ in a durable test over 100 h in the simulated flue gas atmosphere containing 0.02% SO₂.