The　low　cementitious　activity　of　steel　slag　(SS)　limits　its　application　in　cement-based　materials.　The　effects　of　ethanol-diisopropanolamine　(EDIPA)　on　the　hydration　and　mechanical　properties　of　pure　basic　oxygen　furnace　SS　were　investigated.　The　hydration　kinetics　and　pore　structure　of　SS　pastes　incorporated　with　EDIPA　and　the　chelation　of　EDIPA　were　analyzed　to　reveal　the　working　mechanism　of　EDIPA.　The　results　show　that　EDIPA　improves　the　compressive　strength　of　the　hardened　SS　paste　and　greatly　shortens　the　setting　time　of　SS　paste,　which　is　related　to　the　chelation　of　EDIPA.　EDIPA　could　chelate　with　Ca2+,　Al3+,　and　Fe3+　to　form　metal　chelates,　and　the　chelating　ability　of　EDIPA　to　Al3+　and　Fe3+　is　stronger　than　that　of　Ca2+.　The　chelation　of　EDIPA　simultaneously　promotes　the　hydration　and　carbonation　of　aluminate　and　ferrite　phases　(C3A,　C12A7,　and　C2F),　resulting　in　a　large　amount　of　monocarboaluminate　(C(A,　F)CH),　thus　improves　the　hydration　degree　of　SS　paste.　EDIPA　could　refine　the　pore　structure　of　hardened　SS　paste,　which　is　mainly　manifested　as　the　decrease　in　the　amount　of　macropores　and　pore　size,　and　the　increase　in　the　amount　of　small　pores.　The　chelation　of　EDIPA　changes　the　crystal　structure　and　morphology　of　Ca(OH)2,　which　is　potentially　helpful　to　weaken　the　negative　effect　of　Ca(OH)2　on　strength.　This　study　reveals　the　effect　of　chelation　of　EDIPA　on　the　hydration　of　SS,　which　is　a　valuable　guide　for　the　resource　utilization　of　SS.