Abstract: Butt welding of AZ31B magnesium alloy to Q235 steel sheets was conducted by utilizing laser-induced TIG heat source and AZ61 magnesium filler wire. The elemental distribution and tensile strength of the joint were examined by scanning electron microscopy (SEM), electron probe microscope analysis (EPMA), electronic tension machine and optical microscopy. The results show that a satisfied and continuous butt joint of AZ31B magnesium alloy to Q235 steel sheets was obtained. The average tensile load of the joint could reach 3.13 kN/cm, 95% of Q235 base metal. Meanwhile, the interface in the joint mainly consisted of two parts:the middle part of welded seam with diffusion between Mg and Fe; upper and lower surfaces of the steel with wetting as the main form of connection. The diffusion reaction played an important role in bonded interface of magnesium/steel dissimilar metal joint.