The　thermal　fatigue　behavior　and　mechanical　fatigue　behavior　of　board　level　solder　joint　were　investigated　by　experimental　testing　and　numerical　simulation.　And　two　kinds　of　solder　materials,　including　traditional　eutectic　lead-tin　solder　and　SAC305　lead-free　solder,　were　considered.　Results　show　that　the　lead-free　solder　(SAC305)　joint　has　a　longer　thermal　fatigue　lifetime,　but　a　shorter　mechanical　fatigue　lifetime　than　the　eutectic　solder　joint.　Therefore,　the　evolutions　of　inelastic　strains,　including　creep　and　plastic　strain,　caused　by　thermal　fatigue　and　mechanical　fatigue　loading　in　the　solder　joint　were　analyzed　by　a　finite　element　method.　And　the　difference　of　solder　joint＇s　thermal　fatigue　and　mechanical　fatigue　behavior　was　presented.