The development of a new welding method for dissimilar metals is strongly required for weight reduction of automobiles. The most popular and important combination of dissimilar metals is steel and aluminum. The lap joining of steel/aluminum alloy is carried out using the continuous wave-pulse wave (CW-PW) dual-beam YAG laser welding method. The tests are also performed for the lap joints using scanning electron microscopy (SEM),electron probe microzone analysis (EPMA),micro-hardness tester,tensile testing machine. The results show that the CW laser matching the appropriate PW laser for dual-beam laser welding can effectively reduce or avoid the produce of pores,as well as the deeper penetration can be obtained using the low-power CW laser,which expands the scope of the low-power CW laser equipments. In the dual-laser beam welding process,the Fe penetrates into the Al due to the role of pulsed laser. And the irregular hook-like structure produced in the bottom of welding seam,which can enhance the Fe/Al joint strength. A brittle Fe-Al intermetallic compound (IMC) layer formed at the join interface. The shearing strength of the lap joint is 128 MPa,and the morphology is quasi-cleavage fracture.