In　order　to　study　the　effect　of　ferronickel　slag　powder　on　the　permeability　of　cement　soil　the　permeability　of　ferronickel　slag　powder　cement　soil　in　clean　water　environment　and　seawater　environment　was　studied　by　a　pressurized　infiltration　device　and　the　microscopic　analysis　was　carried　out　by　mercury　intrusion　test　and　scanning　electron　microscopeenergy　spectrum　analysis　test.　The　results　show　that　the　addition　of　ferronickel　slag　powder　can　improve　the　impermeability　of　cement　soil　in　both　clean　water　environment　and　seawater　environment　especially　in　seawater　environment.　When　the　content　of　ferronickel　slag　powder　is　more　than　20%　the　effect　of　increasing　the　content　of　ferronickel　slag　powder　on　the　impermeability　of　soilcement　gradually　decreases.　The　ferronickel　slag　powder　can　play　a　microaggregate　effect　and　activity　effect　reduce　the　maximum　pore　size　and　total　porosity　of　cement　soil　and　enhance　its　resistance　to　seawater　erosion.　The　ferronickel　slag　powder　can　make　the　microscopic　structure　of　cement　soil　more　compact　and　promote　the　formation　of　hydration　products　with　low　calciumsilicon　ratio　and　enhance　its　impermeability.　©　2022　Tongji　University.　All　rights　reserved.