The　influencing　mechanism　of　dry-wet　cycling　on　the　NO　x　degradation　and　sterilization　properties　of　photocatalytic　cement　mortar　(PCM)　with　g-C　3　N　4　/CoAl-LDH　was　investigated　through　the　optical　properties,　mineral　composition　of　cement　hydration　products,　pore　characteristics　and　nitrogen　(N)　content.　The　results　indicate　that　as　the　cycle　number　increases,　the　N　content,　band　gap,　Urbach　energy,　NO　x　degradation　rate　and　sterilization　rate　exhibit　periodic　variations,　while　the　peak　intensity　of　CH　(a　cement　hydration　product)　decreases　gradually.　After　10　cycles,　PCM　demonstrates　the　maximum　Urbach　energy,　N　content,　NO　x　degradation　and　sterilization　rate,　as　well　as　the　minimum　band　gap.　At　this　stage,　the　Urbach　energy,　N　content,　NO　x　degradation　and　sterilization　rate　of　PCM　with　1.0　%　g-C　3　N　4　/CoAl-LDH　increase　by　16.2　%,　24.9　%,　15.4　%　and　40.8　%,　while　the　band　gap　and　the　CH　peak　intensity　decrease　by　5.4　%　and　23.4　%,　respectively.　Although　the　NO　x　degradation　and　sterilization　rates　of　PCM　exhibit　periodic　fluctuations　during　the　dry-wet　cycling,　both　of　them　surpass　those　before　the　cycles,　which　shows　the　excellent　photocatalytic　durability　of　PCM.　It　is　expected　that　this　study　not　only　presents　a　new　perspective　on　evaluating　the　durability　of　PCM　＇s　photocatalytic　property,　but　also　provides　an　alternative　approach　for　the　design　of　new　multifunctional　nanocomposites　in　cementitious　materials　for　environmental　pollution　control.