For　the　porthole　hot　extrusion　of　a　thin-walled　tube　based　on　metal　flow,　the　role　of　the　die’s　structure　should　be　focused　on　to　achieve　precision　formation,　especially　for　multi-output　extrusion　and/or　complex　cross-sectional　profiles.　In　order　to　obtain　a　better　metal　flow　balance,　a　multi-output　porthole　extrusion　die　was　developed,　including　some　novel　features　such　as　a　circular　pattern　of　the　portholes　with　a　dart-shaped　inlet　bridge,　a　buckle　angle　in　the　inlet　side　of　the　upper　die,　a　two-step　welding　chamber,　and　a　non-uniform　bearing　length　distribution.　Through　the　use　of　thermo-mechanical　modeling　combined　with　the　Taguchi　method,　the　underlying　effects　of　key　die　features　were　investigated,　such　as　the　billet　buckle　angle,　the　porthole　bevel　angle,　the　depth　of　the　welding　chamber,　and　the　type　of　bridge　on　the　metal　flow　balance.　The　experimental　validation　showed　that　the　developed　numerical　model　for　the　multi-output　porthole　extrusion　process　had　high　prediction　accuracy,　and　was　acceptable　for　use　in　an　industrial　extrusion　with　a　complex　section.　©　2018　by　the　authors.　Licensee　MDPI,　Basel,　Switzerland.