Platinum　is　a　noble　metal　with　excellent　electrical,　optical,　magnetic,　and　thermal　properties　and　has　far-reaching　applications　in　high-temperature　sensing　and　microelectronic　devices.　However,　its　mechanical　properties　at　the　nanoscale,　especially　the　plastic　deformation　mechanism,　still　leave　much　to　be　explored.　In　this　article,　the　tensile　deformation　behavior　of　polycrystalline　platinum　is　investigated　using　a　molecular　dynamics　approach,　and　the　effects　of　strain　rate　and　twinning　on　the　strength　and　deformation　mechanism　of　polycrystalline　platinum　are　studied.　The　results　show　that　an　increase　in　strain　rate　increases　the　strength　of　the　material;　the　plastic　deformation　mechanism　of　polycrystalline　platinum　is　mainly　dominated　by　dislocation　slip　and　phase　transition,　accompanied　by　a　small　amount　of　twin　generation.　The　role　of　twin　boundaries　is　similar　to　that　of　ordinary　grain　boundaries,　which　hinders　the　movement　of　dislocations　and　thus　affects　the　strength　of　platinum　by　refining　the　grains,　and　similar　to　the　positive-reversed　Hall-Petch　relationship,　the　existence　of　a　critical　twin　thickness　makes　the　strength　of　platinum　reach　its　maximum.　Moreover,　it　is　found　that　Shockley　dislocations　are　the　main　type　of　dislocations　in　polycrystalline　platinum　and　play　a　dominant　role　in　the　plastic　deformation　of　platinum.