A laser welding process test was conducted on the lap joint of 0.40mm 0Cr17Ni4Cu4Nb and 0.26mm 3Cr19Ni9Mo2N stainless steel to investigate the microstructure and properties of the welded joint. The structure of the welded specimen was composed of three longitudinal welds created through lap welding. The HKQW-300 laser welding machine was utilized to perform welding joints in an argon atmosphere. The microstructure and mechanical properties of the welded joints were analyzed through tests. The results indicate that，when welding under the process parameters of a laser power of 20W， a defocusing amount of +8mm， a speed of 180mm/min， and argon protection， the weld of the 0Cr17Ni4Cu4Nb and 3Cr19Ni9Mo2N laser welded lap joint exhibits a ferritic weisman structure， with the weld width ranging from 335.3 to 404.0μm. The heat affected zone （HAZ） is narrow. The tensile force of the welded joint exceeds 5.493 9kN， which is better than 73.7% of the tensile force after 3Cr19Ni9Mo2N base metal strengthening， and meets the welding performance requirements of the product. The welding joint demonstrates excellent performance， and the welding seam has no phenomena such as virtual welding and welding penetration. This process has been extensively applied in the development of the pressing belt of the solar wing pressing and releasing mechanism for a satellite.