This　paper　presents　an　investigation　on　the　microstructure　and　mechanical　property　of　Al-alloy　parts　made　by　using　additive　manufacturing　based　on　CMT　(Cold　Metal　Transfer)　welding　technology.　With　the　same　3D　model　and　process　parameters,　a　set　of　hollow　cylindrical　parts　with　100　layers　were　built　up　using　2319,　4043,　5356　aluminum　welding　wires,　respectively.　Then　their　microstructure,　tensile　strength,　and　microhardness　were　tested　and　analyzed　comparatively.　The　layer　bands　characteristics　were　obviously　observed　in　both　2319　and　4043　parts.　In　the　interlayer　region　of　the　2319　parts,　the　segregation　of　alloying　elements　on　the　grain　boundaries　and　inside　the　grains　were　significantly　more　than　that　in　the　fusion　line　region.　For　the　microstructure　of　4043　parts,　the　dendrites　grow　upward　from　the　bottom　without　interruption　in　the　fusion　line　region,　and　the　continuous　growth　structure　was　maintained.　There　is　no　obviously　change　on　the　microhardness　from　the　bottom　to　the　top　because　the　organization　is　uniform　and　there　is　no　significant　difference　in　the　grain　size.　The　ultimate　strength　and　elongation　in　the　horizontal　direction　were　higher　than　those　in　the　longitudinal　direction,　and　the　5356　parts　had　best　mechanical　properties　among　the　three　materials.　Ultrasonic　method　was　also　used　to　measure　the　Young＇s　modulus　of　the　additive　manufactured　parts.　The　Young＇s　modulus　measuring　results　were　accordant　with　the　results　obtained　by　the　mechanical　property　testing,　and　the　error　was　within　3%.　©　2017　Trans　Tech　Publications,　Switzerland.