Three kinds of catalysts, SM700, SM700A and Mn/SM700A, were prepared from swine manure biochar to study their SCR performance at low temperature. The effects of nitric acid treatment and Mn loading on the performance of the catalysts were analyzed. The physicochemical properties of the catalysts were studied by various characterization methods. The results showed that compared with SM700, the specific surface area and total pore volume of SM700A increased, while its average pore size and ash content decreased. When loaded with Mn, the specific surface area and total pore volume of SM700A increased more obviously. Mn/SM700A had the highest activity for NH3-SCR with 63% NOx conversion, 97% N2 selectivity and 77% NH3 consumption at 150 ℃. Compared with SM700A, the adsorbed oxygen content on the surface of Mn/SM700A catalyst and Oα/Oβ increased significantly. The Mn ions on the surface of Mn/SM700A catalyst were extremely dispersed, and Mn4+/Mn3+ had strong redox ability. Therefore, Mn/SM700A showed high catalytic activity for NH3-SCR.