The　main　impurities　in　aluminum　melt　are　hydrogen　and　Al2O3,　which　can　deteriorate　melt　quality　and　materials　performance.　However,　the　diffusion　process　of　H　atoms　in　aluminum　melt　and　the　interactions　among　Al　atoms,　Al2O3　and　hydrogen　have　been　studied　rarely.　Molecular　mechanics　and　dynamics　simulations　are　employed　to　study　the　diffusion　behaviors　of　different　types　of　hydrogen,　such　as　free　H　atoms,　H　atoms　in　H2　and　H+　ions　in　H2O　using　COMPASS　force　field.　Correspondingly,　force　field　types　h,　h1h　and　h1o　are　used　to　describe　different　types　of　hydrogen　which　are　labeled　as　Hh,　Hh1h　and　Hh1o.　The　results　show　that　the　adsorption　areas　are　maximum　for　Hh1o,　followed　by　Hh1h　and　Hh.　The　diffusion　ability　of　Hh1o　is　the　strongest　whereas　Hh　is　hard　to　diffuse　in　aluminum　melt　because　of　the　differences　in　radius　and　potential　well　depth　of　various　types　of　hydrogen.　Al2O3　cluster　makes　the　Al　atoms　array　disordered,　creating　the　energy　conditions　for　hydrogen　diffusion　in　aluminum　melt.　Al2O3　improves　the　diffusion　of　Hh　and　Hh1o,　and　constrains　Hh1h　which　accumulates　around　it　and　forms　gas　porosities　in　aluminum.　Hh1o　is　the　most　dispersive　in　aluminum　melt,　moreover,　the　distance　of　Al-Hh1o　is　shorter　than　that　of　Al-Hh1h,　both　of　which　are　detrimental　to　the　removal　of　Hh1o.　The　simulation　results　indicate　that　the　gas　porosities　can　be　eliminated　by　the　removal　of　Al2O3　inclusions,　and　the　dispersive　hydrogen　can　be　removed　by　adsorption　function　of　gas　bubbles　or　molten　fluxes.　©　2017,　Foundry　Journal　Agency　and　Springer　Nature　Singapore　Pte　Ltd.