Graphene　is　a　significant　reinforcement　in　metal　matrix　composites　by　virtue　of　its　superior　mechanical　properties.　The　cracking　of　metal　crystal　and　the　failure　of　graphene-metal　interface　are　the　main　reasons　for　the　decrease　of　mechanical　properties　of　graphene/metal　composites,　but　the　damage　mechanism　of　that　is　not　clear.　In　this　paper,　a　novel　two-dimensional　microstructure　model　of　graphene/polycrystalline　metal　composites　is　established　by　a　self-developed　structure　modeling　procedure.　According　to　the　actual　structure　of　graphene/metal　composites,　the　numbers,　sizes,　orientations,　arrangements　of　graphene　and　grain　can　be　controlled　respectively.　Moreover,　by　employing　the　method　of　combining　the　crystal　plasticity　finite　element　method　(CPFEM)　and　the　cohesive　zone　model　(CZM),　the　damage　mechanism　of　graphene/aluminum　(Al)　composites　on　polycrystalline　Al　matrix,　graphene-reinforcement　and　graphene-Al　interface　under　tensile　load　is　revealed　from　the　mesoscale　for　the　first　time,　then　the　effects　of　graphene　morphology　and　initial　microcracks　on　the　failure　behavior　and　overall　mechanical　properties　of　graphene/Al　composites　are　fully　captured.　This　study　provides　a　strong　theoretical　support　and　inspiration　for　the　construction　of　graphene/Al　composites　with　excellent　properties.　©　2021　Elsevier　Ltd