Amidst　the　rapid　global　urbanization　and　economic　integration,　coastal　cities　have　undergone　significant　changes　in　urban　spatial　patterns.　These　changes　have　further　worsened　the　complex　urban　thermal　environment,　making　it　crucial　to　study　the　interaction　between　human-driven　development　and　natural　climate　systems.　To　address　the　insufficient　quantification　of　marine　elements　in　the　urban　planning　of　subtropical　coastal　zones,　this　study　takes　Xiamen,　a　typical　deep-water　port　city,　as　an　example　to　construct　a　spatial　analysis　framework　integrating　marine　boundary　layer　parameters.　This　research　employs　interpolation　simulation,　atmospheric　correction,　and　other　techniques　to　simulate　the　inversion　of　land　use　and　Landsat　8　data,　deriving　urban　morphological　elements　and　Land　Surface　Temperature　(LST)　data.　These　data　were　then　assigned　to　500　m　grids　for　analysis.　A　bivariate　spatial　auto-correlation　model　was　applied　to　examine　the　relationship　between　urban　carbon　emission　and　LST.　The　study　area　was　categorized　based　on　the　influence　of　marine　factors,　and　the　spatial　relationships　between　urban　morphological　elements　and　LST　were　analyzed　using　a　multiscale　geographically　weighted　regression　model.　Three　Xiamen-specific　discoveries　emerged:　(1)　the　marine　exerts　a　significant　thermal　mitigation　effect　on　the　city,　with　an　average　influence　range　of　7.94　km;　(2)　the　relationship　between　urban　morphology　and　the　thermal　environment　exhibits　notable　spatial　heterogeneity　across　different　regions;　and　(3)　to　mitigate　urban　thermal　environments,　connected　green　corridors　should　be　established　in　the　southern　coastal　areas　of　outer　districts　in　regions　significantly　influenced　by　the　ocean.　In　areas　with　less　marine　influence,　spatial　complexity　should　be　introduced　by　disrupting　relatively　intact　blue–green　spaces,　while　regions　unaffected　by　the　ocean　should　focus　on　increasing　green　spaces　and　reducing　impervious　surfaces　and　water　bodies.　These　findings　directly　inform　Xiamen’s　2035　Master　Plan　for　combating　heat　island　effects　in　coastal　special　economic　zones,　providing　transferable　metrics　for　similar　maritime　cities.　©　2025　by　the　authors.