Al-Zn-Mg-Cu　alloys　are　widely　used　in　large-scale　structural　components　of　the　aerospace　industry,　but　research　on　wire　and　arc　additive　manufacturing　(WAAM)　of　Al-Zn-Mg-Cu　alloys　is　lacking.　This　research　focused　on　grain　refining　of　Al-Zn-Mg-Cu　alloys　by　adding　TiN　particles　during　WAAM.　The　WAAM　component　was　filled　with　equiaxed　grains　and　the　grain　orientation　became　more　random　because　the　coarse　columnar　grains　were　eliminated.　The　average　grain　size　was　reduced　from　a　value　of　459　mm　to　a　value　of　104　mm.　Heterogeneous　nucleation　by　TiN　particles　was　the　main　grain　refining　mechanism,　and　the　TiN　particles　located　along　the　grain　boundaries　also　helped　prevent　grain　growth.　The　horizontal　and　vertical　elongations　were　increased　by　160%　and　98%,　respectively,　because　of　grain　refinement;　whereas　the　horizontal　tensile　strength　was　increased　by　38.1%.　The　enhanced　mechanical　properties　were　mainly　attributable　to　grain　refinement　and　weakening　of　the　texture　strength.　(C)&　nbsp;2021　The　Author(s).　Published　by　Elsevier　B.V.&　nbsp;