Welding　of　dissimilar　steel/Al　lapped　joints　of　1.5　mm　in　thickness　was　carried　out　by　using　dual-beam　laser　welding　with　side-by-side　configuration.　The　effect　of　the　major　process　parameters　including　the　dual-beam　power　ratio　of　(Rs)　and　dual-beam　distance　(d(1))　on　the　steel/Al　joint　characteristics　was　investigated　concerning　the　weld　shape,　interface　microstructures,　tensile　resistance　and　fracture　behavior.　The　results　show　that　dual-beam　laser　welding　with　side-by-side　configuration　produces　soundly　welded　steel/Al　lapped　joints　free　of　welding　defects.　The　processing　parameters　of　Rs　and　d(1)　have　a　great　influence　on　the　weld　appearance,　the　weld　penetration　in　the　Al　alloy　side　(P2)　and　the　welding　defects.　Variation　in　the　depth　of　the　P2　and　the　locations　at　the　Al/weld　interface　cause　heterogeneous　microstructures　in　the　morphology　and　the　thickness　of　the　intermetallic　compound　(IMC)　layers.　In　addition,　electron　back　scattered　diffraction　(EBSD)　phase　mapping　reveals　that　the　IMC　layer　microstructures　formed　at　the　Al/weld　interface　include　the　needle-like　theta-Fe4Al13　phases　and　compact　lath　eta-Fe2Al5　layers.　Some　very　fine　theta-Fe4Al13　and　eta-Fe2Al5　phases　generated　along　the　weld　grain　boundaries　of　the　steel/Al　joints　are　also　confirmed.　Finally,　there　is　a　matching　relationship　between　the　P2　and　the　tensile　resistance　of　steel/Al　joints,　and　the　maximum　tensile　resistance　of　109.2　N/mm　is　obtained　by　the　steel/Al　joints　produced　at　the　Rs　of　1.50　during　dual-beam　laser　welding　with　side-by-side　configuration.　Two　fracture　path　modes　have　taken　place　depending　on　the　P2,　and　relatively　high　resistance　has　been　achieved　for　the　steel/Al　joints　with　an　optimum　P2.