In this paper, the effects of sulfuric acid treatment of a ZrO₂ support (ZrO₂-S) on the Ca resistance of CeO₂ catalysts were investigated. The results showed that the CeO₂/ZrO₂-S catalyst exhibited much better SCR activity and Ca resistance compared with the CeO₂/ZrO₂ catalyst. To further reveal the Ca resistance mechanism, BET, XRD, Raman, XPS, H₂-TPR, NH₃-TPD and in situ DRIFTS were used to characterize the changes in structure and properties of the CeO₂/ZrO₂ and CeO₂/ZrO₂-S catalysts before and after the Ca deactivation tests. The Ca poisoning of the CeO₂/ZrO₂ catalysts was mainly due to the decrease in specific surface area and surface acidity, the loss of reducibility and the enhanced stabilization of adsorbed nitrate/nitrite species. The treatment of ZrO₂ with sulfate acid led to an increased specific surface area and highly-dispersed Ce species at the catalyst surface. It was also beneficial to inhibiting the transformation of ZrO₂ from the tetragonal to the monoclinic phase. Moreover, it also enhanced the redox properties, Ce³⁺ species ratio, total surface acidity (especially Brønsted acid sites), and adsorption of NH₃ species. The SCR reactions via both Langmuir–Hinshelwood (L–H) and Eley–Rideal (E–R) mechanisms could proceed well even after the CeO₂/ZrO₂-S catalysts were subjected to Ca poisoning.