A　new　dual　beam　laser　deep　penetration　welding　technology　for　lap　joint　of　1.5　mm　thick　aluminum　alloy　and　high　strength　steel　was　explored　in　this　paper,　and　the　effects　of　three　different　beam　energy　ratios　(RS　=0.25,0.33,0.5)　on　weld　formation,　interface　microstructure　and　mechanical　properties　were　studied.　The　result　shows　that　under　certain　conditions　of　other　parameters,　double　beam　laser　deep　penetration　welding　process　can　be　applied　to　lap　joint　of　aluminum　alloy　/　high　strength　steel　with　good　weld　shape　when　RS　=0.25,0.33,0.5.　As　RS　increases　from　0.25　to　0.5,　the　penetration　of　the　weld　reduces　from　575　μm　to　424.2μm,　the　thickness　of　intermetallic　compound　(IMC)　layer　at　the　interface　between　aluminum　alloy　and　weld　metal　reduces　from　3.4　μm　to　2.5　μm,　the　average　microhardness　of　the　IMC　layer　decreases　from　771.1　HV　to　571.9　HV,　the　mechanical　resistance　of　the　joint　raises　from　95.7N/mm　to　115.2N/mm.　When　RS　=0.5,　double　beam　laser　deep　penetration　welding　of　aluminum　alloy　/　high-strength　steel　joints　has　the　highest　mechanical　resistance　of　joints,　because　of　the　relatively　good　plastic　ductility　of　the　joint.　©　2019　Trans　Tech　Publications,　Switzerland.