By　taking　5　mm　thick　5A06　aluminum-magnesium　alloy　as　the　main　researching　object,　the　front　and　back　weld　width　as　the　formation　parameter,　the　significance　of　torch　angle　to　weld　formation　was　studied　by　the　orthogonal　experiment,　the　effect　of　change　of　torch　angle　on　weld　formation　was　studied　from　the　point　of　energy　transfer.　The　result　shows　that　the　influence　of　the　torch　angle　on　welding　formation　is　between　current　and　plasma　gas　flow　rate.　There　is　largest　front　weld　width　when　the　torch　is　perpendicular　to　the　test　plate.　The　back　weld　width　will　be　larger　with　the　torch　angle　increasing.　It　indicates　the　energy　density　on　the　front　surface,　the　relative　position　of　the　highest　temperature　section　and　the　widest　molten　section　will　be　changed　by　torch　angle　change.　The　effect　on　the　back　weld　width　may　be　caused　by　the　interaction　of　sectional　heat　source　deviation　of　different　thickness　direction　and　the　delay　of　heat　transfer.