In order to study the influence of magnetic field on laser welding, a self-made suspended permanent magnet electromagnetic stirring device was placed above the weldment to provide a transverse rotating magnetic field, and a CO2 laser welding test was performed on the pure nickel Ni201 thin plate. After welding, metallographic microscope and scanning electron microscope were used for observation and analysis, and electrochemical workstation was used to conduct electrochemical corrosion test of welded joints. The test results show that, the weldments can be completely welded with different magnetic field intensity, and the welds are formed well, and the inside of the weld is composed of coarse austenite grain.The magnetic field intensity has little effect on the macroscopic appearance of laser welded joints.With the increase of magnetic field intensity, the solidification microstructure of pure Ni201 laser welded joint is gradually refined, and the corrosion resistance of weld metal is gradually improved. The external rotating magnetic field can promote the heat transfer and mass transfer in the molten pool by electromagnetic stirring, increase the supercooling, increase the nucleation rate, make the grain refined, and improve the corrosion resistance of the weld.