The　mechanical　properties　of　electroplated　copper　(Cu)　filled　in　through　silicon　vias　(TSVs)　play　a　key　role　in　the　thermo-mechanical　reliability　of　TSV　packages.　Generally,　it　is　necessary　to　anneal　TSV-Cu　after　electroplating　to　stabilize　its　microstructure.　Different　annealing　conditions　could　affect　the　microstructure　and　deformation　behavior　of　TSV-Cu.　Thermal　and　mechanical　load　during　post-process　and　service　life　could　often　cause　TSV-Cu　reliability　issues　by　its　deformation,　such　as　TSV-Cu　pumping,　interfacial　delamination　and　back　end　of　line　(BEOL)　cracking.　To　understand　the　deformation　behavior　of　TSV-Cu,　this　article　tries　to　obtain　the　constitutive　equations　of　TSV-Cu　under　different　annealing　conditions.　Nanoindentation　tests　and　finite　element　method　(FEM)　inversion　are　used　to　establish　a　constitutive　model　of　annealing　behavior　in　TSV-Cu.　The　power　law　constitutive　models　are　determined　to　describe　the　elastic　and　plastic　behaviors.　Strain　rate　and　annealing　soften　effects　are　both　found　from　the　constitutive　model.　The　microstructures　of　TSV-Cu　are　also　characterized　by　electron　backscatter　diffraction　(EBSD)　to　correlate　with　mechanical　performance.　Grain　size　increased　with　the　increase　of　annealing　temperature,　and　both　hardness　and　yield　strength　follow　the　Hall-Petch　relationship,　which　are　meaningful　for　calculating　the　deformation　of　the　TSV　package　and　improving　the　thermomechanical　reliability　of　the　device.