Glass　fiber-reinforced　polymer　(GFRP)　composites　are　promising　composites　often　utilized　in　coastal　infrastructure　or　used　as　an　alternative　to　steel　reinforcement　in　seawater　sea　sand　concrete　due　to　their　excellent　corrosion　resistance.　Understanding　the　degradation　mechanism　of　GFRP　in　corrosion　environments　is　significant　for　improving　the　long-term　performance　of　GFRP　materials.　This　paper　presented　the　influences　of　seawater　content　and　temperature　on　the　properties　of　GFRP　composites　using　the　molecular　dynamics　method.　The　simulation　results　were　validated　by　existing　experiments　on　mechanical　properties,　interlaminar　strength,　and　microstructures　of　an　accelerated　aging　test　of　GFRP.　The　calculation　results　indicated　that　when　seawater　content　of　the　matrix　increased　from　0%　to　9.09%　at　298　K,　Young＇s　modulus,　shear　modulus,　and　bulk　modulus　decreased　46.72%,　53.46%,　and　41.75%,　respectively.　The　binding　energy　of　GFRP　composites　with　seawater　content　of　2.15%　at　353　K　was　26.46%　lower　than　that　of　unconditioned　GFRP　at　298　K.　It　revealed　that　the　higher　seawater　content　and　temperature　accelerated　the　degradation　of　the　GFRP　composites.　The　investigation　provided　a　comprehensive　understanding　of　the　degradation　mechanism　of　GFRP　in　seawater　environments　and　provided　a　basis　for　the　durability　design　of　GFRP　composites.