Abstract: The fiber laser was used to weld 1mm thick 304 stainless steel sheet, and the influence of different laser welding process parameters on the weld formation was analyzed. The microstructure, growth orientation, and mechanical properties of the weld was analysed by using optical microscope, electron backscatter diffraction and universal material testing machine.The results show that the welding speed, laser power, and beam defocusing amount have a significant impact on the weld formation of 1 mm thick 304 stainless steel sheet. The use of high welding speed, large beam defocus amount and moderate laser power is beneficial to obtain better weld formation. The final optimized laser power is 100W, the welding speed is 6 m/min, and the beam defocusing amount is±10 mm.The weld shows a columnar growth along the < 100> direction, which is mainly composed of austenite γ and incompletely transformed δ ferrite.When the defocusing amount is 10, -10 mm, the joint has higher tensile strength and elongation, and the fracture position is the base material.