The MAG welding of S355 J2 W +N steel, which is commonly used for bogie frame, was carried out by using binary and ternary shielding gas respectively. The influence of ternary shielding gas and binary shielding gas MAG welding on the microstructure and properties of S355 J2 W+N steel was studied by contrast analysis. The result shows that,the weld of S355 J2 W+N steel with ternary gas mixture has better tensile strength,all bending tests of 180° are qualified,has good ductility and toughness. The hardness distribution of each characteristic zone is uniform,the hardness of the ternary gas mixture is slightly higher,and the width of the heat affected zone is 1 mm narrower than that of the binary gas mixture. Whether the weld or the heat affected zone,the impact energy of the welded joint of both gas is higher impact toughness at low temperature. The central weld microstructure of S355 J2 W+N steel is distributed on the columnar grain boundary with binary and ternary protective gas,and the HAZ is composed of ferrite and pearlite with different grain size and strip distribution along the rolling direction. This provides a basis for the use of ternary shielding gas MAG welding for the railway train steering frame.