Abstract: In response to the challenges associated with the synergistic removal of nitrogen oxides (NO_x) and chlorinated aromatic compounds from flue gases generated during steel sintering, waste incineration, and other processes, as well as the issues with existing commercial catalysts, such as a relatively high active temperature window and the tendency to produce highly toxic by-products, a study was conducted on the low-temperature synergistic removal performance of composite metal oxide catalysts, using chlorobenzene (CB) as a surrogate for chlorinated aromatic compounds. The research focused on a CeMnNb ternary composite metal oxide catalyst. Catalyst samples with varying Ce/Nb molar ratios were prepared via the co-precipitation method. The effects of operating parameters, including reaction temperature, ammonia-nitrogen ratio (NSR), O₂ volume fraction, and space velocity, were investigated using a fixed-bed activity testing system. Additionally, X-ray photoelectron spectroscopy (XPS) characterization was employed to explore the structural evolution and sulfur/water resistance mechanisms of the catalyst in the presence of H₂O and SO₂. Results demonstrate that under the optimized condition (a reaction temperature of 280 ℃, volume fractions of NH₃, NO, CB and O₂ of 600×10^-6, 600×10^-6, 300×10^-6, and 8%, respectively, and a space velocity of 60 000 h^-1), the CeMnNb catalyst with a Ce/Mn/Nb molar ratio of 1∶1∶2 can achieve a CB removal efficiency of 97.2% and a NO_x conversion efficiency of 88.3%. Both H₂O and SO₂ are found to inhibit the synergistic removal performance of the catalyst, with a more pronounced inhibitory effect observed when they coexist. Notably, the poisoning effect of SO₂ is irreversible. XPS characterization results reveal that the relative content of Mn⁴⁺ in the catalyst decreases significantly under all three reaction conditions. In the presence of H₂O, Cl formes Mn-Cl bonds with low-valent Mn species. When SO₂ is present, the relative content of surface organic chlorine increases. However, when H₂O and SO₂ coexist, sulfates are readily formed, which is conductive to reduce the deposition of chlorinated compounds.