The　penetration　of　salt　solution　into　graphene　oxide/epoxy　resin　(GO/EP)　will　cause　structural　damage,　decrease　in　mechanical　properties,　and　reduce　service　life.　In　this　study,　molecular　dynamics　method　was　used　to　simulate　the　penetration　of　the　3.5%　NaCl　solution　through　the　GO/EP.　In　order　to　understand　the　effect　of　GO　surface　functional　groups　on　the　barrier　properties　of　the　GO/EP,　a　pure　graphene　model　and　three　kinds　of　GO　models　modified　with　oxygen-containing　functional　groups　(ether,　hydroxyl,　and　carboxyl)　were　established,　respectively.　The　penetration　resistance　of　GO/EP　was　analyzed.　The　type　of　oxygen-containing　functional　group　affects　the　penetration　rate　of　the　salt　solution　and　the　GO/EP　interface　performance.　The　spatial　distribution　and　kinetic　behavior　of　the　salt　solution　were　studied.　The　results　show　that　the　salt　solution　molecules　trapped　in　GO/EP　were　mainly　concentrated　at　the　interface　between　GO　and　EP,　which　is　the　main　reason　for　the　degradation　of　the　GO/EP　interface　performance.　Affected　by　GO,　the　penetration　process　of　ions　can　be　divided　into　multiple　stages,　and　its　motion　state　was　different　depending　on　the　type　of　functional　group.