Abstract: Three heat sources (laser-MIG hybrid, single MIG and single laser) were used to realize the butt connection of 2 mm thick 304 stainless steel plate and 6061 aluminum alloy plate.The wet spreading at steel side, weld center microstructure, steel/Al interfacial compound and tensile properties of the joint under different heat sources were compared.The results show that the front and back spreading effect of the weld is the best under the laser-MIG hybrid heat source, but the molten metal is difficult to spread to the steel side under the single laser heat source.The weld center structure consists of α-Al solid solution and short rod-like Al-Si eutectics under the laser-MIG hybrid and the single MIG heat sources.There are continuously distributed serrated intermetallic compounds at the steel/aluminum interface, the thickness of the interface layer is about 3.6, 3.3 μm, respectively.Under the single laser heat source, the weld center microstructure is equiaxed crystal and many small pieces of precipitates dispersed on the matrix.The compound of the steel / aluminum interface layer is needle shaped, which grows along the aluminum weld, and the thickness is about 5.7 μm.The tensile strength of the joint is the highest under the laser-MIG hybrid heat source, which is 226.5 MPa and up to 53.8% of the aluminum alloy, the fracture surface has a small number of river patterns.The tensile strength of the welded joint under the single laser heat source is the lowest(67 MPa), and most of the fracture area of the weld shows river pattern, which belongs to typical brittle fracture.