To　address　the　problem　of　scarce　freshwater　in　marine　engineering　construction,　seawater　is　used　as　a　substitute　for　freshwater　in　concrete,　offering　both　environmental　and　economic　advantages.　Simulated　seawater　of　varying　concentrations　was　designed　to　assess　its　effect　on　seawater　concrete＇s　drying　shrinkage,　with　corresponding　concrete　samples　prepared.　Drying　shrinkage　and　mass　loss　measurements　were　taken　for　seawater　concrete　(SWC)　at　various　ages.　According　to　the　results　of　Thermogravimetric　Analysis　(TGA),　X-ray　Diffraction　(XRD),　Mercury　Intrusion　Porosimetry　(MIP)　and　Scanning　Electronic　Microscopy　(SEM),　the　effects　of　different　seawater　concentration　on　the　phase　and　content　of　hydration　products,　pore　structure　and　micromorphology　of　SWC　were　analyzed.　The　results　reveal　consistently　higher　drying　shrinkage　and　mass　loss　in　SWC　than　in　ordinary　concrete　(OC).　An　increase　in　seawater　concentration　is　found　to　enhance　the　formation　of　hydration　products,　leading　to　a　refinement　in　the　pore　structure　of　the　concrete.　The　shrinkage　is　positively　correlated　with　the　abundance　of　pores　smaller　than　100　nm　and　is　also　dynamically　influenced　by　the　variety　and　proportion　of　hydration　products.　A　modified　model　derived　from　the　GL2000　and　factoring　in　seawater　concentration,　has　been　introduced　to　forecast　the　drying　shrinkage　in　SWC.　The　insights　garnered　from　this　research　provide　a　foundational　theoretical　groundwork　for　the　construction　of　marine　infrastructure　in　diverse　geographical　settings.