Conventional　asphalt　binder　derived　from　the　petroleum　refining　process　is　widely　used　in　pavement　engineering.　However,　asphalt　binder　is　a　non-renewable　material,　while　waste　cooking　oil　(WCO)　is　a　renewable　original　material,　so　it　can　be　used　as　an　additive　for　asphalt　binder.　Several　studies　found　that　the　WCO　changes　mechanical　properties　of　asphalt　binder.　However,　the　micro　investigation　of　the　modification　of　WCO　is　not　studied.　In　this　paper,　A　reasonable　molecular　structure　for　WCO　is　created　based　on　previous　research　findings　firstly,　which　are　fundamental　and　crucial　for　establishing　the　molecular　model　of　bio-asphalt　binder　with　various　WCO　contents.　Then　the　molecular　dynamics　technology　is　employed　to　investigate　the　mechanical　properties　of　asphalt　binder　with　different　WCO　contents.　The　results　show　that　the　WCO　softens　the　asphalt　binder　increasing　with　its　content,　which　is　consistent　with　the　previous　research,　indicating　that　the　simulated　results　characterize　the　mechanical　properties　of　asphalt　binder　effectively　and　scientifically.