In this paper, the lap welding process of 0.2 mm thick 430 stainless steel is investigated by using a pulsed laser welder, The macroscopic morphology and microstructure of the joint weld cross-section were observed and analyzed, and the effects of different laser powers on the mechanical properties of the joint weld were investigated. The results show that when the welding speed is 10 mm/s, the defocus amount is 0 mm, and the laser power is 130 W, the two plates realize the fusion connection, the weld surface is well formed, and the joint tensile force reaches 2 714 N. The joint molten core area is mainly composed of coarse columnar crystals of ferrite and a small amount of martensite, and it grows perpendicularly to the fusion line towards the center of the weld. The heat-affected zone is narrow at the top and wide at the bottom and consists of coarse equiaxial crystals of ferrite and nodular carbide precipitates. The weld width and depth increase with the increase of laser power. The microhardness of the welded joint is distributed in W type, and there was obvious softening in the heat-affected zone, which was 36% lower than that of the base material. Joint tensile strength increases with the laser power, when the base material achieves complete penetration of the joint, continuing to increase the laser power on the mechanical properties of the joint has little effect, the tensile specimen fracture location occurred in the heat-affected zone near the performance of plastic fracture.