Multi-bead　overlapping　process　of　wire　and　arc　additive　manufacturing　(WAAM)　based　on　the　cold　metal　transfer　(CMT)　is　studied　systematically.　By　using　2319　aluminum　wire　as　the　filling　material,　experiments　are　carried　out　with　the　constant　wire-feed　rate　and　various　travel　speeds.　The　cross　section’s　morphology　of　the　obtained　single　beads　are　separately　fitted　by　the　three　selected　models,　including　the　parabola　model,　arc　model　and　cosine　model.　The　experimental　results　showed　that　both　the　parabola　and　arc　functions　could　accurately　represent　the　bead　profile.　Based　on　parabola　model,　the　single-layer　multi-pass　overlapping　model　is　then　established.　The　theoretical　optimal　overlapping　width　is　calculated　to　be　0.715　times　that　of　the　layer　width.　To　verify　the　accuracy　of　this　model,　single-layer　two-bead　samples　are　produced　with　different　overlapping　rates,　including　the　traditional　flat-topped　overlapping　rate　0.6.　The　experimental　results　showed　that　the　model　proposed　is　more　in　line　with　the　manufacturing　process　of　WAAM　based　on　the　CMT.　When　the　overlapping　rate　is　determined,　the　smaller　the　single-layer　height　is,　the　better　would　the　formed　surface　profile　be,　which　is　propitious　for　the　subsequent　multi-layer　multi-bead　parts　fabricating.　Based　on　the　optimized　overlapping　parameters,　the　multi-layer　multi-bead　part　was　fabricated　with　good　surface　appearance.　And　the　mechanical　properties　in　three　directions　are　analyzed　as　well.　©　2020　Journal　of　Mechanical　Engineering.