CeMn-rare earth tailings catalysts were prepared by hydrothermal method. The results show that the optimum ratio of Ce/Mn is 1:1, and the NO x conversion can reach 90% at the range of 100-300℃. The introduction of Mn improves the dispersion of CeCO 3F on the catalyst surface, exposing more active adsorption sites. In addition, the interaction of MnO x with Ce and Fe in the rare earth tailings promotes redox, which facilitates the oxidation of NO to NO 2. Meanwhile Mn also increases the abundance and stability of NO adsorption species and Lewis acid sites, forming important intermediates such as Mn 4+-ONO 2, NH 4NO 3 and NH 2NO. But the strong oxidizing ability of Mn and the reaction between monodentate nitrate and adsorbed NH 3 results in N 2 selectivity decrease rapidly. Catalysts follow both E-R and L-H mechanism in the NH 3-SCR reaction. Moreover, the excellent redox performance and Lewis acid sites improve the NH 3-SCR catalytic activity together.