In　this　study,　a　new　type　of　photocatalytic　composite　material　“sulfur-doped　carbon　nitride/　calcined　magnesium　aluminum　hydrotalcite　(S-g-C3N4　/　MgAl-CLDH)”　was　synthesized　and　loaded　on　cement　mortar　through　internal　doping.　The　nitrogen　oxide　(NOx)　degradation　and　hydration　performance　of　photocatalytic　mortar　were　tested.　The　results　show　that　when　the　photocatalyst　dosage　is　less　than　5%　(mass　fraction),　the　S-g-C3N4　/　MgAl-CLDH　content　is　directly　proportional　to　the　NOx　degradation　rate　of　mortar.　When　the　photocatalyst　dosage　exceeds　5%,　the　NOx　degradation　performance　of　mortar　begins　to　decrease　due　to　agglomeration.　In　addition,　due　to　the　nucleation　effect　of　nanomaterials,　the　incorporation　of　an　appropriate　amount　of　S-g-C3N4　/　MgAl-CLDH　significantly　improves　the　early　(1　d)　hydration　degree　of　cement.　However,　due　to　its　water　absorption　and　agglomeration　phenomenon,　excess　S-g-C3N4　/　MgAl-CLDH　reduces　the　later　hydration　degree　of　cement.　When　the　photocatalyst　dosage　is　7%,　the　28　d　strength　of　cement　mortar　significantly　decreases　compared　with　the　control　mortar.　In　addition,　an　appropriate　amount　of　S-g-C3N4　/　MgAl-CLDH　(3%)　can　improve　28　d　strength　of　mortar　due　to　its　micro-filling　effect.　©　2024　Bulletin　of　the　Chinese　Ceramic　Society　Press.　All　rights　reserved.