At　present,　the　connection　of　steel/aluminum　joints　has　been　widely　used　in　industrial　fields　such　as　aerospace,　marine　and　automotive.　Although　the　joints　with　excellent　performance　can　be　obtained　by　the　solid　phase　welding　methods　such　as　explosion　welding　and　friction　welding,　the　production　process　is　complicated　and　the　efficiency　is　low,　and　the　practical　application　is　limited.　Laser　welding　has　attracted　a　lot　of　attention　from　researchers　because　of　its　advantages　of　high　energy　density,　small　welding　deformation　and　fast　welding　speed.　However,　in　the　single-beam　laser　welding　process,　there　are　problems　such　as　high　joint　assembly　precision,　excessive　energy　density,　and　easy　formation　of　depressions　in　the　weld.　The　newly　developed　laser-MIG　(Metal　Inert　Gas)　hybrid　welding　not　only　retains　the　advantages　of　laser　welding,　but　also　fully　exploits　the　advantages　of　MIG　welding,　improves　weld　formation,　improves　the　stability　of　the　welding　process,　and　helps　solve　the　single-beam　laser　welding　problems.　In　this　paper,　the　laser　deep　penetration　welding　process　of　5.5　mm　thick　E36　steel　and　6　mm　thick　5083　aluminum　alloy　butt　joint　was　studied　by　laser-MIG　composite　welding　heat　source.　Compared　with　the　single　laser　welding　process,　the　influence　of　wire　feed　speed　on　the　welded　steel/aluminum　joint,　joint　interface　structure　and　joint　mechanical　properties　was　studied.　The　results　show　that　the　laser-MIG　composite　deep-melt　welding　can　obtain　good　steel/aluminum　butt　joint　performance.　At　a　laser　power　of　3.25　kW,　a　wire　feed　speed　of　1.5　m　/　min,　a　laser　offset　of　0.5　mm　and　a　defocus　of　0　mm,　the　tensile　strength　of　the　steel/aluminum　butt　joint　is　as　high　as　85.0　MPa.　Laser-MIG　hybrid　welding　can　improve　the　dent　defects　of　a　single　laser　welded　steel/aluminum　butt　joint.　The　amount　of　acicular　Fe4　Al13　phase　in　the　intermetallic　compound　was　significantly　reduced,　and　the　resistance　of　the　steel/aluminum　joint　was　increased　from　8.6　kN　to　12.7　kN.　©　2019　Trans　Tech　Publications,　Switzerland.