A　thermodynamics-based　damage　mechanics　rate　dependent　constitutive　model　is　used　to　simulate　experiments　conducted　on　thin　layer　eutectic　SnAgCu(SAC)　solderjoints.　The　non-damage　constitutive　is　measured　by　bulk　tensile　test.　The　relationship　between　true　stress　and　strain　is　sigma=85.260.3536.　Damage　evolution　equation　is　proposed　based　Lemaitre　ductile　damage　theory　and　the　constant　in　the　equation　is　measured　by　unloading　elastic　modulus　method.　The　damage　evolution　equation　is　D=1.0689　epsilon　P-0.0008.　Simulation　(using　software　Ansys　9.0)　of　shear　test　of　solder　joint　between　Cu　sticks　employing　damage　mechanics　rate　independent　constitutive　is　uniform　to　practicable　test.