Abstract: 0.1 mm thick 316L stainless steel plate is mainly used for manufacture of bipolar plate, the main component of hydrogen fuel cell. In the manufacture process, it is necessary for lap welding of the sheet. The lap welding of 0.1mm thick 316L stainless steel bipolar plate was carried out by the single-mode fiber laser welding technology. The morphology of the front and section of the welded joint was observed, and the influence of different process parameters on the weld forming and the mechanical properties of the welded joint were analyzed. The results show that the weld surface quality is good, the welded joint can achieve penetration connection; the weld depth and weld width are directly proportional to the laser power and inversely proportional to the welding speed. In the case of penetration connection, the strength of the weld meets the strength requirements of the bipolar plate. The microhardness of the welded joint is distributed in M type.