Abstract: 316L stainless steel was welded by TIG under magnetic field. The effect of excitation current on the microstructure and properties of 316L stainless steel TIG welded joint was studied by combining optical microscope, electron scanning microscope and microhardness testing. The results show that with the increase of the exciting current, the penetration effect get better, the more serious the collapse and the wider the weld zone, the greater the hardness reduction rate of the welded joint. Compared with that of the base metal, the hardness reduction rate of welded joint at excitation currents of 1 A, 2 A and 3 A is 9.8%, 10.4% and 15.3%, respectively, with 2 A being the optimum excitation current. With the increase of the ex citation current, the grain size in the weld area increases, especially when the excitation current increases from 2 A to 3 A, the grain size coarseness becomes more significant, and the maximum grain size in the weld area increases from 170 μm to 350μm. The weld area is austenitic structure and vermicule ferrite, and there are obvious transition zones and heat affected zones.