Nanocrystalline　copper　(Cu)　is　considered　to　be　one　of　the　best　interconnected　material　in　integration　circuit　(IC)　industry,　because　of　its　ultra-low　resistivity　and　high　mechanical　stability.　Mechanical　properties　of　nanocrystalline　Cu　are　completely　different　from　those　of　bulk　monocrystalline　Cu.　These　properties　are　of　high　importance　in　the　assessment　of　the　thermo-mechanical　reliability　of　the　interconnected　IC　structure.　To　investigate　the　effects　of　the　grain　sizes　and　temperature　on　the　mechanical　properties　of　nanocrystalline　Cu,　molecular　dynamics　simulations　of　uniaxial　tensile　test　are　performed　in　this　study.　The　results　show　that　the　elastic　modulus　of　nanocrystalline　Cu　with　grain　sizes　of　4.65-12.41　nm　gradually　increases　with　the　increase　of　the　mean　grain　sizes,　the　corresponding　flow　stress　concurrently　increases,　and　the　flow　stress　is　proportional　to　the　square-root　of　the　grain　size,　which　satisfies　the　inverse-Hall-Petch　relation.　Furthermore,　the　elastic　modulus　linearly　decreases　with　the　increase　of　temperature.　The　coupled　effect　of　the　flow　stress,　strain　rate　and　temperature　were　elaborated　by　the　Arrhenius　hyperbolic　sinusoidal　model.　Meanwhile,　the　deformation　activation　energy　of　nanocrystalline　Cu　for　various　grain　sizes　were　obtained.　All　of　the　tensile　simulation　tests　confirmed　that　the　mechanism　of　plastic　deformation　for　nanocrystalline　Cu　with　4.65-12.41　nm　grain　sizes　is　mainly　specific　to　the　grain　boundary　sliding　and　grain　rotation.　The　dislocation　nucleation　and　migration,　which　is　usually　the　deformation　mechanism　of　plasticity　for　macroscopic　materials,　is　no　longer　the　dominant　factor　for　nanocrystalline　Cu.