With　the　urgent　demand　for　the　reduction　of　harmful　element　in　electronic　product,　lead-free　solder　is　considered　to　be　potential　brazing　alloy　due　to　the　toxicity　of　lead.　The　major　effect　of　long　time　exposured　under　solder　Sn-Pb　base　solder　are　proven　to　increase　nervous　system　disorder　risk.　Sn3Ag0.5Cu　is　a　normal　lead-free　solder　product　with　the　content　of　Sn　beyond　90%.　It　can　lead　to　the　formation　of　β-Sn　after　remelting.　Crystal　c-axis　of　β-Sn　is　0.3181nm,　crystal　a-axis　and　b　is　0.5832nm.　The　crystal　orientation　will　close　to　each　other　after　reflow　soldering.　Sn　crystals　showed　strong　anisotropy　because　of　the　body-centered　tetragonal　structure　and　Recrystallization　begins　due　to　the　thermal　mechanical　fatigue.　Recrystallization　caused　by　thermal　mechanical　fatigue　could　deteriorate　solder　joint　mechanical　property.　Because　it　is　unclear　about　mechanism　of　recrystallization,　it　is　necessary　to　investigate　the　thermal　and　mechanical　force　factors　respectively　in　order　to　study　stress　affection　to　recrystallization　performance.　In　this　paper,　inhomogeneous　evolution　of　the　microscopic　structure　and　crystal　orientation　with　different　quantity　of　deformation　were　studied.　All　the　samples　were　machining　from　lead-free　welding　rod　by　wire　cut　electrical　discharge　machining.　Experiments　were　conducted　with　tensile　specimens　made　by　SAC305　at　a　speed　of　0.2um/s　per　second　on　tensile　machine.　Before　and　after　specimens　approach　tensile　strength,　different　samples　with　different　load　times　10　seconds,　50　seconds,　150　seconds　and　250　seconds　were　analyzed　by　scanning　electron　microscope,　and　electron　back-scattered　diffraction,　and　so　as　the　fracture　region.　The　surface　grain　characteristics　and　the　fracture　mechanisms　were　discussed.　Inhomogeneous　evolution　of　different　deformation　were　investigated.　The　experimental　results　show　that　crystal　misorientation　in　adjacent　grains　were　getting　larger　with　increasing　deformation.　Located　different　area　of　tensile　specimens,　the　distribution　of　low　angle　grain　boundaries　and　high　angle　grain　boundaries　showed　significant　difference.　It＇s　believed　that　with　high　angle　grain　boundaries　are　transformation　of　low　angle　grain　boundaries　caused　by　the　activation　process　of　the　slip　systems　and　high　density　dislocation　movement.　Central　area　of　specimens　shows　that　no　obvious　recrystallization　means　the　number　of　movable　dislocations　are　not　sufficient　to　transform　low　angle　grain　boundaries　to　high　angle　grain　boundaries.　©　2017　IEEE.