Phosphogypsum　(PG),　an　industrial　waste　containing　phosphorus,　has　resulted　in　accumulation　and　environ-mental　pollution　because　of　its　shallow　utilization　rate　worldwide.　In　this　paper,　unpretreated　PG　is　incorporated　into　magnesium　oxysulfate　cement　(MOSC)　as　an　insert　fine　aggregate　at　different　dosing　levels.　The　performance　of　the　resulting　mortar　is　evaluated　by　testing　workability,　volume　stability,　mechanical　properties,　water　resistance,　and　sustainability.　Results　show　that　PG　improved　the　water　resistance,　the　long-term　compressive　strength,　and　the　microstructure　of　MOSC.　XRD/Rietveld　analysis　and　TG-DSC　demonstrated　that　the　incorpo-ration　of　PG　inhibited　the　crystallization　of　Mg(OH)2　and　promoted　the　formation　of　5　Mg(OH)2.MgSO4.7H2O　(5.1.7　phase).　Besides,　some　PG　undergoes　morphological　changes　that　may　disrupt　the　strength　of　MOSC.　PG-MOSC　has　the　potential　for　environmental　sustainability　because　of　its　low　carbon　emissions　and　efficient　toxic　immobilization.　The　paper　provides　ideas　and　a　reference　for　the　resource　utilization　of　PG.