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• Toxicity effects of lead salt species on Mn-Ce/Cu-X catalyst were investigated. • Pb species might primarily occupy the active site of Mn and Cu species. • PbCl 2 and PbNO 3 species predominantly affected the Brønsted acid sites. • PbSO 4 and PbCO 3 species mainly impacted the adsorption of NO + O 2. For the sintering flue gas in steel industry, selective catalytic reduction (SCR) of NO x using NH 3 at low temperature in the presence of heavy metals is still a challenge. In this study, the toxicity effects of lead salt species (PbCl 2 , Pb(NO 3) 2 , PbSO 4 , PbCO 3) on Cu-exchanged zeolite X doped with Mn-Ce catalysts (MCCX) were investigated. All catalysts exhibited poor low-temperature SCR performance within 75–225 °C after Pb poisoning, and the poisoning effects of PbCl 2 , Pb(NO 3) 2 , PbSO 4 and PbCO 3 on MCCX catalyst varied. The PbSO 4 had the most serious poisoning on MCCX catalyst, while PbCO 3 had poisoning effect on catalysts even at 300 °C. Lead species poisoning had bad impact on the structure of zeolite X on MCCX catalyst, and caused some agglutination of Cu species. Likewise, the Pb species might primarily occupy the active site of Mn and Cu species and influence the redox property of catalysts, thereby obstructing the redox and oxidation cycles on catalysts surface. In addition, the PbCl 2 and PbNO 3 species predominantly affected the Brønsted acid sites and occupied the Cu or Mn active sites, inhabiting the absorption and conversion of nitrites and nitrates on the catalyst surface. Moreover, PbSO 4 and PbCO 3 species mainly impacted the adsorption of NO + O 2 and the conversion of nitrites and nitrates on the catalysts. [ABSTRACT FROM AUTHOR]