Wire　arc-directed　energy　deposition　(WADED)　has　shown　great　advantages　and　potential　in　fabricating　large-scale　aluminum　(Al)　alloy　components.　However,　WADED　Al　alloys　typically　exhibit　low　strength　and　reliability　due　to　pore　defects　and　lack　of　work　hardening　or　precipitation　strengthening.　This　study　utilized　a　combination　of　laser　shock　peening　(LSP)　and　annealing　to　regulate　the　microstructure　of　WADED　Al-Mg4.5Mn　alloy　and　enhance　mechanical　properties.　The　effects　of　LSP　and　annealing　on　phase　composition,　pore　distribution,　and　microstructures　at　multiple　scales　were　systematically　investigated　to　reveal　the　mechanical　property　improving　mechanism.　The　results　demonstrated　that　LSP-induced　plastic　deformation　formed　a　defect-free　zone　by　closing　near-surface　pore　defects.　LSP　created　the　hardened　layer　with　gradient　mechanical　properties　by　inducing　gradient　changes　in　grain　size,　the　number　of　lowangle　grain　boundaries　(LAGBs),　and　dislocation　density　along　the　depth　direction.　The　annealing　process　promoted　grain　coarsening　and　reduced　excessive　dislocations　and　LAGBs,　weakening　the　work　hardening　effect　caused　by　LSP.　Furthermore,　the　high-density　dislocations　and　high　stored　energy　generated　by　LSP　accelerated　the　recrystallization,　facilitating　growth　of　near-surface　grains.　The　defect-free　zone,　dislocation　strengthening,　and　LAGBs　strengthening　were　responsible　for　the　increase　in　strength,　while　the　synergistic　deformation　between　hardened　layers　and　soft　core　facilitated　maintaining　excellent　elongation.　The　strength　and　elongation　of　WADED　Al　alloy　can　be　synergistically　improved　by　balancing　the　effects　of　LSP　and　heat　treatment.　(c)　2024　Published　by　Elsevier　Ltd　on　behalf　of　The　editorial　office　of　Journal　of　Materials　Science　&　Technology.