The　macro-mesoscopic　joint　fatigue　model　containing　hardening　particles　and　crystal　characteristics　is　established　to　study　the　effect　of　the　hardening　particles　and　the　grain　orientation　on　fatigue　properties　of　an　aluminum　alloy　friction　stir　welding　(FSW)　joint.　The　macroscopic　model　is　composed　of　the　weld　nugget　zone,　thermo-mechanically　affected　zone,　heat-affected　zone,　and　base　material,　according　to　the　metallurgical　morphology　and　hardness　distribution　of　the　joint.　Cyclic　stress　and　strain　data　are　used　to　determine　the　material　properties.　The　fatigue　parameters　used　in　the　calculation　of　cyclic　stresses　and　strains　are　obtained　with　the　four-point　correlation　method.　The　mesoscopic　models　of　different　zones　are　inserted　into　the　joint　macroscopic　model　as　submodules.　The　models　containing　the　information　of　hardening　particles　and　grain　orientation　are　established　with　crystal　plasticity　theory　for　the　grains　and　isotropic　hardening　rule　for　the　hardening　particles.　The　effects　of　hardening　particles　and　grain　orientation　on　the　stress　and　strain　responses　are　discussed.　The　simulation　results　show　that　high-angle　misorientation　of　adjacent　grains　hinders　the　stress　transfer.　The　particle　cluster　or　cracked　particles　intensify　the　stress　and　strain　concentrations.