Fatigue　properties　of　friction　stir　welding　(FSW)　butt　joints　for　aluminum　alloy　AA2219　were　researched　by　experimental　analysis　and　numerical　simulation.　The　FSW　joint　model　including　the　representative　volume　elements　(RVE)　was　built　based　on　the　metallographic　morphologies,　micro　hardness　profile　and　local　mechanical　properties.　The　morphology　and　distribution　of　the　matrix　and　precipitation　strengthening　phases　were　included　in　the　RVE　of　the　joint.　The　stresses　and　plastic　strains　of　the　precipitation　strengthening　phases　and　matrix　were　estimated　with　the　mixture　rules.　Stress　concentration　happens　at　the　strengthening　phases　and　neighbouring　metal　matrix.　Plastic　strain　concentration　appears　at　the　interface　of　the　matrix　and　strengthening　phases.　The　fatigue　weak　areas　in　the　FSW　joint　were　obtained　with　the　joint　model.　The　results　show　that　the　estimated　fatigue　weak　areas　are　close　to　the　experimental　results　and　the　errors　of　predicted　fatigue　life　are　basically　within　2　factors　based　on　the　FSW　joint　model.　(C)　2017　Elsevier　Ltd.　All　rights　reserved.