Nanolaminated　metal/graphene　composites　can　have　many　special　mechanical　properties,　thanks　to　a　high　density　of　interfaces.　Even　though　the　interface　effect　is　a　key　mechanism　for　the　propagation　of　dislocations　in　nanolaminated　metal/graphene　composites,　it　is　not　well　understood.　In　this　paper,　simulations　of　the　molecular　dynamics　of　nanolaminated　polycrystalline　aluminum/graphene　(PAl/Gr)　composites　are　performed.　The　results　provide　insight　into　the　grain-size　effect　on　plastic　flow　stress　of　nanolaminated　PAl/Gr　composites　and　the　underlying　mechanism.　Extended　dislocations　are　found　to　dominate　the　plastic　deformation　of　the　PAl/Gr　composites.　Both　the　PAl/Gr　interface　and　the　Al　grain　boundaries　(GBs)　interact　with　the　dislocations.　Three　dislocation　propagation　forms　are　observed　in　the　PAl/Gr　nanolaminated　composite　based　on　the　Al　grain-size.　By　decreasing　the　laminate　thickness,　the　dislocation-GB　interaction　can　transition　to　a　dislocation-graphene　interaction.　When　the　Al　layer　thickness　is　smaller　than　the　in-plane　grain　size,　the　strain-hardening　capability　is　increased　due　to　greater　ability　of　the　dislocation/graphene-interface　to　store　dislocations　than　the　GBs.　Besides,　geometrically　necessary　dislocations　are　induced　because　of　the　deformation　gradient　between　the　graphene　and　Al　grains,　which　lead　to　back-stress　strengthening　and　thus　strain　hardening.　Accordingly,　a　confined　layer　slip　mechanism,　which　considers　back-stress,　is　used　to　predict　the　flow　stress　of　the　PAl/Gr　composites.