As　a　class　of　emerging　contaminants　in　marine　environments,　organophosphate　esters　(OPEs)　have　attracted　increasing　attention　of　environmental　scientists　and　policymakers　due　to　their　ubiquity　and　ecotoxicity.　However,　little　is　known　about　the　environmental　geochemical　behaviors　of　OPEs　in　seawater　of　the　South　China　Sea　(SCS).　In　this　study,　the　concentration,　composition,　pollution　source,　and　ecological　risk　of　twelve　typical　OPEs　were　analyzed　in　the　surface　seawater　of　the　northern　SCS　between　August　and　September　2021.　The　results　showed　that　five　out　of　twelve　OPEs　were　detectable　with　the　total　concentration　of　five　OPEs　(Σ5OPEs)　ranging　from　7.17　to　67.6　ng/L　in　seawater.　Chlorinated　OPEs　(Cl-OPEs)　were　the　predominant　OPEs,　with　a　mean　concentration　of　18.4　ng/L,　accounting　for　more　than　69.8　%　of　Σ5OPEs.　Among　the　detected　congeners,　tris(2-chloroethyl)　phosphate　(TCEP)　was　the　most　abundant　OPE　(mean:　14.8　ng/L,　56.2　%),　followed　by　triethyl　phosphate　(TEP)　(mean:　7.75　ng/L,　29.5　%)　and　tris(1-chloro-2-propyl)　phosphate　(TCIPP)　(mean:　2.07　ng/L,　7.87　%).　Principal　component　analysis　and　Spearman　correlation　analysis　indicated　that　terrestrial　inputs,　atmospheric　deposition,　and　shipping　activities　were　the　potential　sources　of　OPEs　in　the　northern　SCS.　The　ecological　risk　assessment　revealed　that　TCEP　posed　low　threats　to　algae　and　low　ecological　risks　were　predominantly　observed　from　the　mixture　of　OPEs.　This　work　provides　a　basis　for　further　investigation　into　the　environmental　behavior,　toxicity,　and　risk　of　OPEs　in　the　SCS　and　facilitates　a　better　implementation　of　effective　management　actions.　©　2024　The　Authors