Nitrogen　oxide　(NOx)　is　a　typical　atmospheric　pollutant　that　harms　the　environment　and　human　body,　and　selective　catalytic　reduction　with　NH3　(NH3-SCR)　is　one　of　the　most　effective　technologies　to　deal　with　its　emissions　at　present.　In　this　work,　the　Gd-Mn-Ti　composite　oxides　are　anchored　on　waste　coal　fly　ash　(CFA)　as　catalyst　for　the　reduction　of　NOx　by　the　NH3-SCR　technology.　The　developed　0.2Gd-Mn-Ti/CFA　catalyst　presents　above　90%　de-NOx　efficiency　from　120　to　330　°C　with　a　wide　temperature　window.　The　reasons　can　be　ascribed　to　the　facts　that　the　introduction　of　appropriate　Gd　can　increase　the　acid　sites,　improve　the　redox　environment　and　elevate　the　content　of　surface　Mn4+　and　chemical　adsorption　oxygen　(Oα).　In　addition,　the　interaction　between　Gd-Mn-Ti　composite　oxides　and　between　active　components　and　carrier　also　plays　a　positive　role　for　the　excellent　reaction　activity.　Additionally,　both　E-R　and　L-H　mechanisms　are　included　in　the　NH3-SCR　reaction　over　Gd-Mn-Ti/CFA　catalyst.　This　work　opens　up　a　new　way　for　the　utilization　of　waste　CFA,　and　provides　a　reference　for　the　design　and　preparation　of　Mn-based　low-temperature　de-NOx　catalysts　with　wide　temperature　windows.　©　2022　Elsevier　B.V.