Low-temperature selective catalytic reduction (SCR) denitrification is an important technology for the end treatment of flue gas and enhancing sulfur resistance of catalysts is a challenge demanding prompt solution in the field of low-temperature SCR. Here, a Mn-HAP catalyst for nitrogen removal at low temperature (100-200 ℃) was successfully synthesized by co-precipitation method using hydroxyapatite (HAP) as carrier and Mn as an active component, and then its denitrification performance and resistance to fight against metal sulfate and ammonium sulfate poisoning were studied. The results showed that the sulfur resistance of the catalyst could be improved to a certain extent by using HAP as Mn active substance carrier. When the reaction temperature was 140 ℃, the denitrification efficiency of the SCR catalyst reached 100%. Meanwhile, the effect of metal sulfate on the denitrification activity at low temperature was more significant than that of ammonium sulfate, and the denitrification efficiency under the two sulfate species at 120 ℃ was reduced by 37.40% and 8.83%, respectively, as compared with that of fresh catalyst. Different characterization analysis indicated that different surface sulfur species could reduce the specific surface area and change the oxidation state of active Mn to various degrees. The main reason for catalysts deactivation is that the metal sulfate can significantly decrease the proportion and oxidation-reduction performance of Mn⁴⁺. Therefore, this study provides an important direction for improving the sulfur resistance of SCR catalysts.