Polycrystalline　copper　is　considered　by　the　industries　to　be　the　best　TSV　electroplating　material　and　other　interconnected　structure　material　because　of　its　ultra-low　resistivity,　high　conductivity,　low　electro-migration　rate　and　good　compatibility　with　the　multilayer　interconnects　process.　Its　mechanical　properties　are　completely　different　from　the　bulk　monocrystalline　copper,　these　properties　are　critically　vital　to　evaluate　the　thermomechanical　reliability　of　TSV　and　interconnected　structure　in　3D　packaging.　To　investigate　the　effect　of　the　work　temperature　and　grain　size　on　the　mechanical　properties　of　polycrystalline　Cu,　The　MD　simulations　of　uniaxial　tensile　test　are　performed.　The　results　showed　that　the　elastic　modulus　gradually　increases　with　the　augment　of　the　mean　grain　size,　and　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.　It　also　turned　that　the　elastic　modulus　decreases　with　increasing　of　ambient　temperatures,　the　flow　stress　is　negatively　correlated　with　the　temperature.　From　all　the　tensile　simulation　tests,　it　was　confirmed　that　the　mechanism　of　plastic　deformation　for　polycrystalline　copper　with　4.65-9.31nm　grain　sizes　is　mainly　the　grain＇s　rotation　and　grain-　boundary　sliding,　the　dislocation　nucleation　and　migration　is　no　longer　the　dominant　factor　of　plastic　deformation.