Abstract: Shield metal-arc welding（SMAW） and gas tungsten arc welding（GTAW） methods were used to weld 1 MnCrMoNi alloy steel for marine engineering, the microstructure, microhardness, tensile and impact properties of the welded joints were investigated. The results show that the microstructure of the heat-affected zone of the two kinds of welded joints consists of ferrite, granular bainite and pearlite, and the M-A component is locally present in SMAW joint. The microstructure of the SMAW joint welded seam are favourably staggered acicular ferrites and a small amount of granular bainite, and the microstructure of the bottom layer of the GTAW joint welded seam consists of fine acicular ferrite and some granular bainite,and the surface layer is a mixture of coarse bulk ferrite, fine acicular ferrite, pearlite and granular bainite. The hardness of the heat affected zone of the two welded joints is not much different from that of the base metal, and the welded seam hardness is much higher than those of the base metal and the heat affected zone. The tensile strength of the welded joints is the same as than that of the 1 MnCrMoNi alloy steel base metal, and the tensile fracture position is the base metal, and the performance totally accords with the requirements of practical engineering applications. The impact toughnesses of the welded seam and heat affected zone of the two welded joints are bigger than the standard value at the test temperature, the toughness is qualified.