The　asphalt　binder　in　pavement　mixtures　frequently　exposed　to　oxygen　and　undergoes　daily　temperature　cycles.　This　results　in　oxidation　and　dehydrogenation　of　its　chemical　composition,　leading　to　the　aging　of　the　asphalt　binder.　The　aging　process　of　asphalt　binder　directly　affects　the　pavement＇s　service　life　and　therefore　has　been　subject　to　intense　research　regarding　the　chemical　composition　and　rheological　properties.　However,　the　microscopic　reasons　for　these　changes　are　not　yet　clear.　A　molecular　dynamics　(MD)　simulation　is　employed　to　investigate　the　aging　process　from　a　microscale　perspective.　Six　molecular　models　for　six　asphalt　binders　at　different　aging　states　are　created　based　on　the　ratio　of　saturates,　aromatics,　resin　and　asphaltene　(SARA)　as　well　as　carbonyl　and　sulfoxide　indexes　to　investigate　the　effect　of　aging　on　physical　properties　of　asphalt　binder　have　been　investigated.　The　results　explain　the　mechanism　for　hardening　of　asphalt　binder　during　aging　process,　and　find　some　correlations　between　micro　and　macro　phenomena.　(C)　2018　Elsevier　Ltd.　All　rights　reserved.