<p>To explore the denitration mechanism of iron–vanadium/activated carbon (Fe–V/AC) catalysts in ammonia-selective catalytic reduction (NH₃-SCR), the physicochemical properties of Fe–V/AC catalysts were characterized. The denitration activities of the Fe–V/AC catalysts in the range of 150–300&#xa0;°C were evaluated. The increase in denitration temperature leads to the highest and fastest recovery rate of NO conversion in the 10Fe–15V/AC catalyst. However, more metal oxides were attached to the catalyst surface as the V loading increased, and the accumulation occurred. The surface-active components are FeO, Fe₂O₃, Fe₃O₄, VO₂, and V₂O₅. In addition, the increase in the V loading induced a series of modification effects. A large amount of Fe³⁺ was reduced to Fe²⁺, and a large amount of V⁴⁺ was oxidized to V⁵⁺. The surface oxygen species (O_α) were transformed into lattice oxygen (O_β). The presence of a large amount of V species deteriorated the pore-structure parameters and destroyed the oxygen-containing functional groups. Increasing the V loading can effectively increase the Lewis acid sites, thereby promoting NH₃ adsorption and NO reduction and increasing the stretching vibration of weakly adsorbed ammonia species on the catalyst. The NH₃ adsorption process produces a notable increase in the concentration of monodentate nitrite (NH₄⁺). The NH₃-SCR denitration mechanism of the Fe–V/AC catalyst includes reaction gas adsorption, catalytic denitration of metal active components, and gas desorption.</p>