As　a　kind　of　air　pollutant,　nitrogen　oxide　cause　serious　human,　environmental　and　ozon　layer　issues.　Non　-ammonia　catalytic　materials　have　a　more　simple　and　environments-friendly　reaction　process　without　second-ary　pollution,　and　therein　are　considered　as　an　ideal　catalyst　for　the　reduction　of　NO　in　the　flue　gas　of　cement　kilns.　In　this　paper,　the　denitrification　performance　of　coal　gasification　slag　was　investigated　systematically　at　different　temperatures　and　oxygen　concentrations　in　cement　kiln　flue　gas.　The　transformation　mechanism　of　NO　was　studied　by　analyzing　the　changes　of　surface　element　valence　state,　the　adsorption　and　desorption　of　NO　and　the　formation　of　intermediate　during　the　reaction　process.　The　results　show　that　the　conversion　rate　of　NO　in　flue　gas　can　reach　83.49　%　when　the　temperature　is　1000　degrees　C　and　the　oxygen　concentration　is　1　%.　The　charged　ionic　groups　are　generated　by　the　isomorphous　substitution　of　Fe3+　in　coal　gasification　slag,　and　play　an　important　role　in　the　decomposition　of　NO　as　active　components.　It　can　increase　the　number　of　surface　oxygen　vacancies,　and　accelerate　the　fracture　of　N-O　bonds　into　active　components;　Meanwhile,　Fe3+　could　coordinate　with　O-　and　NO-　(generated　by　N-O　fracture)　to　form　Fe3+-O-　and　Fe3+-NO-,　which　can　be　decomposed　into　Fe2+,　N2　and　O2　at　high　temperature.