Abstract: To explore the influence law of laser welding technology on the welding forming effect of ultra-thin SUS304 stainless steel sheet (thickness of 0.15 mm), this study selected welding process conditions with laser power ranging from 280W to 320W and welding speed within the range of 4m/min to 5m/min, and implemented lap laser welding experiments. The study focused on analyzing the characteristics of weld formation under the changes of these process parameters, and conducted in-depth analysis of the microstructure and mechanical properties of the welding joints with the best forming effect. The experiment found that excessive laser power will lead to excessive heat accumulation and cause weld burn-through; on the contrary, insufficient laser power will weaken the penetration ability and cause incomplete fusion of the weld. Both of these situations are not conducive to the improvement of the bearing capacity of the welded joint. The study pointed out that under the process conditions of laser power of 320W, welding speed of 5m/min, and heat input of 3.8J/mm, the tensile shear strength of the welded joint is the best. In addition, the fractures of joints under all test conditions occur in the heat-affected zone. The tensile load of the optimally formed joint reaches 1.67kN, which is equivalent to 86.5% of the tensile load of the base metal of 1.93kN, and shows the characteristics of ductile fracture.