Abstract: The 6 mm thick Q450NQR1/Q355GNHD dissimilar steel plates were welded by MAG automatic welding and CHW-55CNH welding wire. The microstructure of different areas of the welded joint was analyzed, and the hardness and tensile properties of the joint were tested. The corrosion properties of different areas of the joint were studied by electrochemical corrosion and salt spray corrosion tests. The results show that the weld of Q450NQR1/Q355GNHD dissimilar steel is well formed without obvious defects such as undercut, incomplete penetration and incomplete fusion. The hardness of the weld is higher than that of the base metals, the tensile strength of the joint is between that of the two base metals, the tensile fracture is at the base metal of Q355GNHD, which is ductile fracture. The neutral salt spray corrosion results show that the joint and the base metals at both sides are seriously corroded, and thick corrosion products are accumulated on the surface area, and the galvanic corrosion effect is not obvious. The corrosion resistance of the weld zone of the joint is lower than that of the base metal, and the corrosion resistance of the heat affected zone is equivalent to that of the base metals.