Purpose　-　The　purpose　of　this　paper　is　to　develop　a　portable　all-position　welding　robot　for　the　welding　of　intersected　pipes.　Design/methodology/approach　-　A　complete　procedure　is　adopted　to　conduct　the　design.　The　task　and　motion　of　the　robot　are　analyzed　and　a　mathematical　description　of　the　pose　and　position　of　the　welding　tool　is　given.　Based　on　that,　three　representative　types　of　robot　are　chosen　in　the　type　synthesis　of　mechanism.　Two　new　indices　proposed　to　evaluate　required　properties　of　the　robot,　along　with　the　traditional　dexterity　index,　are　chosen　to　be　the　criteria　in　the　dimension　synthesis　of　mechanism.　Through　the　optimization　by　genetic　algorithm,　the　best　robot　in　type　and　dimension　is　determined　after　comparison　on　their　performances.　Finally,　the　prototype　is　developed.　Findings　-　The　paper　finds　a　new　robot　for　welding　intersected　pipes.　Originality/value　-　A　new　robot　is　introduced　for　the　welding　of　intersected　pipes.　A　complete　design　procedure　is　adopted　to　conduct　the　design.　Two　new　indices　are　constructed　for　evaluating　the　required　properties　of　this　robot.