Understanding　plastic　deformation　behaviour　is　key　to　optimising　the　mechanical　properties　of　nano-polycrystalline　layered　composites.　This　study　employs　the　molecular　dynamics　(MD)　simulation　to　comprehensively　investigate　the　effects　of　various　factors,　such　as　grain　sizes,　strain　rates,　and　the　interlayer　thicknesses　of　the　intermetallic　compounds　(IMCs),　on　the　plastic　deformation　behaviour　of　nano-polycrystalline　Al/Mg　layered　composites.　Our　findings　reveal　that　the　influence　of　grain　size　on　deformation　behaviour　is　governed　by　the　strain　rate,　and　an　increase　in　grain　size　is　inversely　proportional　to　yield　stress　at　low　strain　rates,　whereas　it　is　positively　proportional　to　tensile　stress　at　high　strain　rates.　Moreover,　an　optimal　thickness　of　the　intermediate　layer　contributes　to　enhanced　composite　strength,　whereas　an　excessive　thickness　leads　to　reduced　tensile　strength　due　to　the　fewer　grain　boundaries　(GBs)　available　for　accommodating　dislocations.　The　reinforcing　impact　of　the　intermediate　IMCs　layer　diminishes　at　excessive　strain　rates,　as　the　grains　struggle　to　accommodate　substantial　large　strains　within　a　limited　timeframe　encountered　at　high　strain　rates.　The　insights　into　grain　sizes,　strain　rates,　and　interlayer　thicknesses　obtained　from　this　study　enable　the　tailored　development　of　nanocomposites　with　optimal　mechanical　characteristics.