Abstract: The experiments of laser penetration welding-brazed for magnesium alloy and steel were carried out with AZ31 magnesium alloy and Q235 steel as base metals,achieving a hybrid joint of welding and brazing.The microstructure and mechanical properties of butt joints were investigated by optical microscopy,scanning electron microscope and tensile testing.At the upper part of the joint,there is little melting or dissolving of steel due to high interface temperature.At the lower part of the joint,there is no indication of melted steel,the molten magnesium alloy,as filler metal,to form a successful joint of Mg/Fe dissimilar alloys by wetting and spreading.In particular,at 0.6mm laser offset,the average tensile strength could reach a maximum of 182 MPa,about 81% that of AZ31 Mg alloy.The fluctuation of tensile strength was the lowest in all laser offsets.