The　chromium　(Cr)　pollution　of　soil　has　recently　gained　a　lot　of　attention　for　the　demand　of　environmental　protection.　One　of　its　main　resources　is　from　the　landfill　of　the　chromium　containing　sludge　(CCS)　that　produces　from　reduction–precipitation　treatment　of　the　Cr(VI)　wastewater.　In　this　work　we　provide　an　improved　alkaline　oxidation　calcination　(AOC)　treatment　for　CCS,　which　achieves　high　Cr　recovery　efficiency　at　relatively　low　calcination　temperature　and　oxygen-rich　conditions.　The　leaching　risk　of　the　final　residue　is　much　reduced　compared　to　the　conventional　calcination.　It　reveals　that　by　using　air　flow　the　oxidation　efficiency　is　effectively　improved　to　a　value　of　near　to　∼　90　%　at　450　℃.　The　thermal　analyses　of　the　reaction　suggest　that　Cr　(III)　in　CCS　transforms　to　chromite　at　the　temperature　range　of　340–450　℃,　which　ensure　the　subsequent　oxidation.　On　the　other　hand,　it　reveals　that　at　higher　temperature　(　500　℃)　it　will　produce　Ca–Fe　oxides　which　are　confirmed　to　be　dissolved　in　the　leachate　of　the　toxicity　test.　The　concentration　of　Cr　(III)　increases　obviously,　which　could　be　associated　with　the　release　of　Cr(III)　that　doped　into　Ca–Fe　oxides　as　solid　solution.　The　transformations　of　the　CCS　components　during　the　AOC　process　are　depicted　in　detail.　The　method　proposed　here　enables　high　oxidation　efficiency　of　CCS　and　meanwhile　avoids　the　environmental　risk　of　final　residue.　©　2023　Elsevier　B.V.