Additive　manufacturing　technology　is　a　novel　approach　for　the　development　of　the　modern　industry.　Additive　manufactured　aluminium　(Al)　becomes　the　hotspot　of　current　research　in　order　to　achieve　the　high　precision　products.　However,　the　additive　manufactured　Al　parts　easily　generate　void　defects　due　to　the　poor　fluidity　and　low　density　of　the　materials,　which　in　turn　affects　the　mechanical　properties.　This　paper　studies　the　damage　behavior　of　additive　manufactured　Al　parts　with　void　defects　under　tensile　load　in　a　mesoscale　by　using　a　two-dimensional　rate-dependent　crystal　plasticity　theory.　The　stress-strain　curves　and　the　plastic　damages　of　single　crystal　and　bicrystal　with　void　defects　are　determined　with　different　combinations　of　crystal　orientations　and　loading　conditions.　It　is　found　that　the　mechanical　properties　of　additive　manufactured　aluminium　severely　depend　on　the　crystal　orientations　and　shapes　of　void　defects.　(C)　2018　Elsevier　Ltd.　All　rights　reserved.