This study investigated the impact of metal doping on the DeNOx and anti-poisoning performance of MnOx/m-ZrO2. The DeNOx performance increases from 96% to nearly 100% by Co or Sm doping. However, the anti-poisoning performance was enhanced more by Sm doping, and the DeNOx performance remained at 90.97% after water and sulfur compound poisoning. The improved redox performance caused by the interaction between Sm and Mn resulted in more acidic sites that aid in the adsorption of NOx and NH3, and the presence of Sm effectively inhibits the formation of sulfate and ammonium sulfate, thus enhancing the DeNOx and anti-poisoning performance.