In　order　to　save　fuel　consumption　by　reducing　the　weight　of　automobile　body,　the　use　of　aluminum　alloys　has　a　great　advantage.　However,　how　to　join　aluminum　alloys　with　steels　becomes　a　big　problem　in　the　assembly　lines.　Cold　metal　transfer　(CMT)　is　a　promising　joining　process　for　steel/Al　dissimilar　materials.　To　evaluate　the　shear　strength　and　to　investigate　the　failure　modes　of　CMT　brazed　lap　joints　of　dissimilar　materials,　both　experimental　observation　and　numerical　simulation　are　performed.　A　numerical　model　for　the　failure　criteria　of　the　interface　layer　failure　between　steel　and　aluminum　is　developed.　The　interface　layer　of　CMT　brazed　lap　joint　can　be　modeled　by　the　interface　element.　The　failure　stress　and　failure　energy　at　the　interface　element　are　proposed　as　the　failure　criteria　for　the　prediction　of　shear　strength　of　CMT　lap　joints.　If　steel　sheet　thickness　becomes　thicker,　stress　distribution　and　concentration　at　interface　layer　elements　have　some　change　and　shear　strength　at　the　interface　layer　can　be　improved.　Then　the　failure　occurring　at　the　interface　element　may　transfer　to　the　fusion　line　at　the　side　of　the　aluminum　alloy　sheet.　©　(2013)　Trans　Tech　Publications,　Switzerland.