Simulated　marine　material　ultra-high　performance　concrete(UHPC)was　prepared　by　incorporation　of　different　contents　of　chloride,　and　the　critical　endogenous　chloride　ion　content　of　steel　bar　corrosion　in　UHPC　was　studied　by　three　electrochemical　methods,　linear　polarization,　electrochemical　impedance　spectroscopy　and　cyclic　polarization.　The　pore　structure　of　UHPC　was　studied　by　the　nitrogen　adsorption　and　desorption　test.　Finally,　the　chloride　ion　diffusion　model　derived　from　Fick＇s　second　law　was　used　to　predict　the　service　life　of　UHPC.　The　results　show　that　the　current　specification　for　chloride　in　sea　sand　concrete　is　not　suitable　for　UHPC　,　the　critical　endogenous　chloride　content　in　UHPC　is　1.2%　to　1.9%　of　cement　mass,　and　its　conservative　value　is　significantly　greater　than　the　standard　limit　for　ordinary　concrete　chloride　ion.　The　internal　structure　of　UHPC　is　extremely　dense,　and　the　porosity　at　the　late　hydration　stage　is　greatly　reduced.　Compared　with　ordinary　UHPC,　the　total　pore　volume　of　simulated　marine　ground　material　UHPC　is　smaller,　showing　a　more　compact　microstructure.　The　durability　of　UHPC　made　with　simulated　marine　materials　is　slightly　decreased　compared　with　the　ordinary　UHPC,　but　still　has　an　excellent　protection　property　of　reinforcement.　The　predicted　service　life　can　reach　more　than　100　years　with　the　cover　thickness　of　only　15　mm.　©　2022　Southeast　University.　All　rights　reserved.