Abstract: With a 6 mm thick 316L stainless steel plate as the object, the magnetic field assisted laser-arc composite welding study was carried out. By changing the magnetic field intensity, the weld appearance, cross-sectional morphology,weld microstructure and weld corrosion behavior were analyzed. The results show that the alternating magnetic field increase the penetration ability of laser-arc hybrid welding, and the penetration state changes from local incomplete penetration to good penetration. In addition, the microstructure of the weld seam is significantly homogenized. On the one hand, the difference in Cr element between the austenite in the arc zone and the laser zone is obviously reduced, on the other hand, the grain size difference between the arc zone and laser zone is obviously reduced. The alternating magnetic field improves the corrosion resistance of the joint weld. It increases the self-corrosion potential and reduces the current density, thus significantly reduces the density of pitting pits in the weld. The study indicates that for laser-arc hybrid welding, the introduction of magnetic field is beneficial for improving the penetration ability and weld uniformity, which improves the formability and corrosion performance of the weld.