Abstract: The laser-MAG hybrid butt welding was carried out for the 16 mm thick 921A ship steel test plate. The microstructure, mechanical properties and corrosion resistance of the welded joint were analyzed. The results show that the welded joint consists of arc welding zone, laser zone and heat affected zone, and the microstructure of the arc welding zone and laser zone is composed of acicular ferrite, a small amount of eutectoid ferrite and some granular bainite. The coarse-grained zone of the heat affected zone is composed of lath martensite, and the fine-grained zone is composed of fine and uniform martensite. The average hardness of the welded joint is about 310 HV, and the highest hardness is 355 HV, which meets the requirements of acceptance standards. The tensile fracture of the welded joint is located in the base metal region,indicating that the tensile property is better than that of the base metal. The impact resistance of the weld zone is lower than that of base metal, but the fracture form is typical ductile fracture, indicating that the joint still has good toughness. The corrosion resistance of the weld zone is better than that of the heat affected zone and the base material, indicating that the welded joint has good corrosion resistance.