The　numerical　simulation　of　tensile　fracture　behavior　on　Al-Cu　alloy　friction　stir-welded　joint　was　performed　with　the　Gurson-Tvergaard-Needleman　(GTN)　damage　model.　The　parameters　of　the　GTN　model　were　studied　in　each　region　of　the　friction　stir-welded　joint　by　means　of　inverse　identification.　Based　on　the　obtained　parameters,　the　finite　element　model　of　the　welded　joint　was　built　to　predict　the　fracture　behavior　and　tension　properties.　Good　agreement　can　be　found　between　the　numerical　and　experimental　results　in　the　location　of　the　tensile　fracture　and　the　mechanical　properties.