To　promote　the　recycling　of　industrial　waste　residues　in　the　reinforcement　of　foundation　soil,　the　anti−seawater　erosion　of　cement　soil　with　ferronickel　slag　powder　in　the　marine　environment　was　studied.　Specifically,　this　paper　employed　ferronickel　slag　powder　to　partially　replace　the　cement.　Then,　the　apparent　morphology,　unconfined　compressive　strength,　and　nuclear　magnetic　resonance　(NMR)　tests　were　performed　on　specimens　of　cement　soil　with　ferronickel　slag　powder　soaked　in　purified　water　and　seawater.　The　research　results　reveal　that　with　the　rise　in　the　content　of　ferronickel　slag　powder,　the　erosive　effect　of　seawater　on　cement　soil　weakens,　while　the　compressive　strength　of　cement　soil　increases　first　and　then　decreases.　With　an　excessive　amount　of　ferronickel　slag　powder　added　to　the　cement　soil,　its　chemically　active　effect　decreases,　leading　to　a　decrease　in　the　strength　of　the　cement　soil.　When　the　admixture　of　ferronickel　slag　powder　in　cement　soil　is　45%,　it　achieves　good　performance.　The　addition　of　ferronickel　slag　powder　improves　the　plasticity　of　cement　soil.　The　higher　the　content　of　ferronickel　slag　powder,　the　greater　the　failure　strain　and　residual　strength　of　the　cement　soil.　Microscopic　studies　indicate　that　with　the　increase　in　the　content　of　ferronickel　slag　powder,　the　pores　in　the　cement　soil　become　smaller　and　smaller,　the　total　pore　volume　decreases,　the　continuity　of　the　pore　size　distribution　improves,　and　the　structure　becomes　more　compact,　thus　enhancing　the　erosion　resistance　of　cement　soil.　©　2023　by　the　authors.