In　this　paper,　a　model　composed　of　a　macroscopic　finite　element　(FE)　model　coupled　with　a　microscopic　phase　field　(PF)　model　was　constructed　to　investigate　the　Al　alloy　microstructure　evolution　during　wire　arc　additive　manufacturing　(WAAM).　First,　the　relationships　between　single　layer　process　parameters　and　the　resulting　deposition　geometries　(width　and　height)　were　investigated.　A　three-dimensional　FE　model　was　built　to　calculate　the　thermal　distribution　and　temperature　gradient　under　different　process　parameters.　These　results　were　then　fed　into　a　PF　model　to　obtain　the　microstructure　corresponding　to　each　set　of　process　parameters.　A　bridge　was　constructed　by　this　method,　starting　from　the　WAAM　process　parameters　and　yielding　the　microstructure　throughout　solidification.　The　simulated　results　showed　that　the　primary　dendrite　arm　spacing　(PDAS)　decreased　slightly　with　current　increases,　but　the　substrate　moving　speed　had　a　more　obvious　impact　on　PDAS,　which　rose　significantly　with　increased　substrate　speed.　Finally,　metallographic　examination　and　energy　dispersive　spectroscopy　tests　were　conducted　on　specimens　fabricated　by　WAAM　with　different　process　parameters,　to　verify　the　simulated　PF　results.　The　simulated　morphology　and　size　of　dendrites　were　in　good　agreement　with　experimental　results.　©　2021　The　Society　of　Manufacturing　Engineers