NOx　emission　from　the　cement　industry　have　received　much　attention.　In　order　to　reduce　the　NOx　emission　in　cement　kilns,　nickel　slag　was　used　to　prepare　the　non-ammonia　denitrification　material,　and　a　denitrification　mechanism　was　proposed　in　this　study.　The　results　showed　that　the　denitrification　material　prepared　at　pH　7　exhibited　the　best　denitrification　performance.　At　low　temperature,　the　highest　denitrification　performance　was　achieved　between　200　and　300　°C　with　a　NO　decomposition　rate　of　approximately　40%.　Then,　the　NO　decomposition　rate　increased　as　the　temperature　increased,　reaching　over　95%　above　700　°C.　The　physicochemical　characteristics　showed　that　the　material　had　the　highest　specific　surface　area　and　the　highest　relative　Fe　content,　which　benefited　the　denitrification　performance.　The　divalent　iron　of　the　denitrification　material　was　considered　the　active　site　for　the　reaction,　and　trivalent　iron　was　not　conducive　to　denitrification　performance　at　a　low　temperature　range.　After　the　denitrification　reaction,　the　Fe3+/Fe2+　increased　from　0.89　to　1.31.　The　proposed　denitrification　mechanism　was　the　redox　process　between　divalent　iron　and　trivalent　iron.　This　study　not　only　recycles　industrial　waste　to　reduce　solid　waste　pollution　but　also　efficiently　removes　nitrogen　oxides　from　cement　kilns　without　ammonia.　©　2023　by　the　authors.